J. Nannoplankton Res. 37 (2–3), 2017, pp.77–112 © 2017 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA

77

Oligocene-Pliocene taxonomy and stratigraphy of thegenus Sphenolithus in the circum North Atlantic Basin:
Gulf of Mexico and ODP Leg 154
Jim Bergen*
Paleo at the Hill Country, Brenham, TX 77833, USA; *jbnanno@att.net

Eric de Kaenel
DPR, chemin sous la Roche 4b, 1185 Mont-sur-Rolle, Switzerland; edekaenel@bluewin.ch

Stacie Blair
Blair Biostratigraphy, 13126 Park Forest Trail, Cypress, TX 77429; stacie.blair81@gmail.com

Todd Boesiger
ALS Global, 5929 Lee Circle, Lincoln, NE 68506; tboesig@gmail.com

Emily Browning
BP America, RD-Exploration NWD, 200 Westlake Park Blvd, Houston, TX 77079; Emily.Browning@bp.com
Manuscript received 12th September, 2016; revised manuscript accepted 20th May, 2017

Abstract Sphenolithus is secondary only to the genus Discoaster in Cenozoic nannofossil biostratigraphy, notablyof primary importance for the Oligocene to Early Miocene. The research presented herein provides a framework
for Oligocene to Middle Pliocene Sphenolithus, where gradations between individual taxa and their stratigraphic
ranges are presented. Integration of schemes from BP, Amoco and Arco Vastar, to form a single composite Neogene
calcareous nannofossil framework for the Gulf of Mexico basin, began around the turn of the century with focus
on refining taxonomic concepts to solve stratigraphic discrepancies between the heritage schemes. Further study
and bioevent calibration was accomplished through analyses of deep-water wells in the Gulf of Mexico along withresearch grounding the integrated framework to the “astronomical clock” of ODP Leg 154 back into the middle Early
Oligocene at an average sample resolution of 21 kyr. Forty-two species are considered herein, in addition to themorphologically-similar Ilselithina fusa. Thirteen new species are introduced. Sphenolithus peartiae and Sphenolithus
distentus are emended. Clarification of taxonomic concepts by the use of morphologic groups is supplemented withidentification tables, drawings, and light photomicrographs. Iterative processes, in terms of size, are stressed.

Keywords Sphenolithus, nannofossils, Oligocene, Miocene, taxonomy, Gulf of Mexico
1. Introduction
One of the major achievements in biostratigraphy within
BP after the mergers with Amoco and Arco Vastar was
the integration of the Cenozoic calcareous microfossil
biostratigraphies for the Gulf of Mexico (GoM) Basin,
which were developed independently within the three
heritage companies. The resulting Neogene framework,with a biostratigraphic resolution of 141 kyr is, to ourknowledge the only fully astronomically-tuned industrial
framework. A twelve-year research program on Ocean
Drilling Program (ODP) Leg 154 on the Ceará Rise in thewestern equatorial Atlantic (Figure 1) provided a cyclostratigraphic-based age model for the Early Oligocene(30.679Ma) through Early Pleistocene (1.595Ma). This
internal research program also included work on the
Oligocene-Miocene boundary Global Stratotype Section
and Point (GSSP) in Italy (de Kaenel & Bergen, 2008;
Bergen et al., 2009; de Kaenel & Villa, 2010). Researchon the Leg 154 material was conducted at an average sample resolution that approximates that of a precession cycle.
The details of our age model with sample depths and ages
will be presented in Bergen et al. (in prep.).
We consider taxonomic clarification of species necessary before publication of the astronomically-tuned
BP Gulf of Mexico Neogene chronostratigraphic chart(GNATTS). The realization of the need for more precise
and standard taxonomic concepts in the Gulf of Mexico
was first demonstrated by a taxonomic working groupformed in late 1990’s to discuss the genus Pseudoemiliania and the Discoaster quinqueramus lineage. The seriesof five manuscripts produced for this volume are looselyorganized around the taxonomic groupings considered bya second industrial nannofossil working group (the Gulf
Coast Taxonomic Equivalency Project), focused on the
GoM Miocene, which convened three times in Houston
from 2011 to 2012. Our five papers are focused on the

78

Bergen et al.

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G7GMG#*G7GMG#V

P)DD)I;H??!B=BP)% /(YE 4!<)= ZYYJ YGG*G7GMG#N)$'&!$"(#(%&!

P)% /G/E 4!<) $,Z

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N!W) 9)W<HJ V%RA<

3?!C!+H+
S:RHCHP)% /&(E 4!<)= Y,&IY,Y

Figure 1: Locality map of materials used in this publication

stratigraphically-significant genera Helicosphaera, Sphenolithus, and Discoaster (three papers) and introduce
BP-heritage GoM taxonomy and stratigraphy for the firsttime. Other taxa significant to the Gulf of Mexico Neogene
discussed in these papers include the genera Amaurolithus,
Calcidiscus, Camuralithus, Catinaster, Ceratolithus,
Coccolithus, Coronocyclus, Cryptococcolithus, Cyclicargolithus, Dictyococcites, Ilselithina, Minylitha and Reticulofenestra.
2. Materials and methods
Lithic materials used for this study are from outcrop, core,
and well cuttings. ODP Leg 154 collections at the International Ocean Discovery Program (IODP) repository in
Bremen (Germany) provided the main source of public
core material. Other collections used were: (1) DSDP Leg
68 (Hole 502) in the western Caribbean Sea; (2) ODP Leg
149 (Holes 899B & 900A) in the northeastern Atlantic
Ocean; (3) ODP Leg 101 (Hole 628A) in the western North
Atlantic Ocean; (4) the base Neogene GSSP section near
Lemme-Carrioso in northern Italy; and (5) theTrinidad “Bolli
collection” sampled by H.M. Bolli (1957) (See Figure 1).
Many important Oligocene-Miocene nannofossil taxa havebeen published from the Bolli collections (Bramlette& Riedel, 1954; Bramlette & Wilcoxon, 1967; Bukry,
1971b; Bukry & Percival, 1971; Gartner, 1967; Hay et al.,
1967; Martini & Bramlette, 1963; Roth, 1970), but none in
the past 45 years. Three Trinidad samples are used herein:(1) JS 20, Globorotalia opima opima Zone, Zone NP24;(2) KR9397, Catapsydrax stainforthi Zone, Zone NN3; and(3) Bo267, Catapsydrax dissimilis Zone, Zone NN2. Deepwater Gulf of Mexico well materials came predominantly
from ditch-cutting samples. Specimens photographed fromwells in Guyana and the Nile Delta, Egypt are also illustrated.
The following stratigraphic abbreviations are used:
LO (lowest occurrence) and HO (highest occurrence);abundance modifiers are: R (regular) for LRO and HRO,
F (few) for LFO and HFO, C (common) for LCO and HCO.

The objective of this work is to clarify taxonomic
concepts and present the GoM stratigraphy developed
over the past five decades from the three BP heritage
companies (Amoco, Arco Vastar and BP), not to compare our results to other published stratigraphies of the
GoM Basin or research on ODP Leg 154. The geologic
ages derived from sampling of ODP Leg 154 are maintained at three decimal precision through the manuscript
for consistency; error given on ages is the differencein age for the next sample analyzed upwards or downwards in the composite section. Links to supplementarymaterials will be provided on the publication’s website
and include biometrics (http://ina.tmsoc.org/JNR/JNRcontents.htm).
3. Biostratigraphy
The primary zonation (NP/NN Zones) referred to herein
is Martini (1971), although the zonation (CP/CN Zones)of Okada & Bukry (1980) is also referred to within the
text. Any new zones or emendations are presented by deKaenel et al. (2017) and Blair et al. (2017) in this volume.
Four Sphenolithus species are used in zonal definitions for the Lower Oligocene to lower Middle Miocene(NP23-NN5): S. ciperoensis, S. distentus, S. belemnos and
S. heteromorphus. The LO of S. ciperoensis defines thebase of Zone NP24 and its age is determined with highreliability from Leg 154 by both de Kaenel and Bergen.
We believe discrepancies in this age determination (seeAubry, 2014) are largely taxonomic, although the holotype is clearly illustrated. Conversely, the holotype of
S. distentus is highly problematic, making taxonomic
clarification necessary for accurate zonal determinations.
Its LO defines the base of Zone CP18, which subdivides
Zone NP23; its HO defines the base of Zone NP25 (alsobase Subzone CP19b). The top of Zone NP25, defined by
the HO of S. ciperoensis, is easily delineated because it
represents the extinction of the lanceolate sphenoliths.
A Zone NP26, defined by de Kaenel et al. (2017) from

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

Taxon

79

Event

Zone
Martini 71

Age
(Ma)

Error1(Ma)

Rel2

Hole-Core-Sec.
cm-cm

Depth
(rmcd)3

S. abies

HO

NN16

3.510

0.017

10

926C-11H-2, 138-139

108.85

S. moriformis

HO

NN16

3.531

0.008

10

926C-11H-3, 55-56

109.52

S. neoabies

HO

NN16

3.531

0.008

10

926C-11H-3, 55-56

109.52

S. abies

HFO

NN16

3.666

0.019

-

926C-11H-6, 30-31

113.77

S. heteromorphusHO

top NN5

13.4080.028

10926A-29-2, 99-101

292.19S. heteromorphus

LCO

NN4

17.3830.010-

928B-28-1, 0-2

272.64

S. apoxis

HONN417.3470.009

10928B-27-CC, 30-32

271.42

S. apoxis

HFO

NN4

17.425

0.018-

928B-28-1, 110-111

273.74S. heteromorphus

LFO

NN4

17.6520.020-

928B-28-4, 55-57

277.69S. belemnos

HO

top NN3

17.6830.011

5928B-28-4, 117-118

278.31

S. heteromorphus

LO

NN3

17.7910.020

9928B-28-6, 40-41

280.54

S. belemnos

HRO

NN3

17.8310.020

10928B-28-6, 118-119

281.32

S. procerus

HO

NN3

18.6120.020

9926B-37-4, 90-92

371.42

S. paratintinnabulum

HO

NN3

18.6120.020

9926B-37-4, 90-92

371.42

S. dissimilis

HO

NN3

18.7680.015

6926B-38-1, 70-72

376.31

S. disbelemnos

HO

NN3

18.7680.015

9926B-38-1, 70-72

376.31

S. calyculus

HO

NN3

19.3310.018

5926B-39-5, 95-96

392.26

S. belemnos

LO

top NN2

19.4140.019

7926C-39-6, 30-31

394.52

S. cometa

HRO

NN2

19.8320.020

6926B-41-1, 65-66

404.86

S. conicus (>7)

INC

NN2

20.291

0.020-

926B-42-3, 5-6

416.96

S. microdelphix

HO

NN2

21.3620.020

5926B-45-5, 80-81

449.71

S. disbelemnos

HCO

NN2

22.0670.020-

928B-35-2, 125-126

342.89S. disbelemnos

LCO

NN2

22.2880.019-

926B-48-4, 120-122

477.61

S. dissimilis

LO

NN2

22.6580.019

6926B-49-5, 50-51

488.02

S. capricornutus

HO

NN1

22.9980.020

6926B-50-4, 90-92

496.61

Sphenolithus spp.

ACME

NN1

22.9980.020-

926B-50-4, 90-92

496.61

S. delphix

HO

NP26

23.0930.021

10926B-50-6, 45-46

499.17

S. conicus

ACME

NP26

23.2530.019-

926B-51-2, 115-116

503.46

S. ciperoensis

HO

top NP25

24.2150.022

10926B-53X-5, 70-71

526.72

S. bulbulus

HO

NP25

24.2480.015

4926B-53X-5, 143-145

527.44

S. capricornutus

LO

NP25

24.2810.023

5926B-54X-1, 1-2

529.73

S. bulbulus

HRO

NP25

24.3650.019

10926B-54-2, 65-66

531.87

S. avisHO

NP25

24.4080.043

5926B-54-3, 30-31

533.02

S. ciperoensis

HCO

NP25

24.4560.048-

926B-54-3, 145-146

534.17

S. peartiae

HO

NP25

24.6830.019

8926B-55-1, 80-81

540.12

S. triangularis

HO

NP25

24.7000.017

8928B-41-5, 75-76

403.33

S. ciperoensis (>6)

HO

NP25

24.8000.041

5926B-55-3, 60-61

542.92

S. tawfikii

HO

NP25

25.0470.029

3925A-26-4, 70-71

568.05

S. distentusHO

top NP24

26.1260.016

7926B-58-7, 13-14

577.44

S. avisHRO

NP24

26.6270.040

8926B-60-3, 5-6

590.77

S. predistentus

HO

NP24

26.9260.041

10926B-61-3, 20-21

600.62

S. peartiae (>7)

HO

NP24

27.2180.048

10926B-62X-2, 133-134

609.84

S. pseudoradians

HO

NP24

28.0920.045

4926B-64X-4, 75-76

631.56

S. apoxis (>8)

HO

NP24

28.0920.045

6926B-64X-4, 75-76

631.56

S. akropodus (<8)

HO

NP24

28.6550.043

7928B-50X-2, 5-6

485.49485.96

S. ciperoensis (>6)

LO

NP24

28.6830.050

5928B-50X-2, 52-53

S. akropodus (<8)

HRO

NP24

29.1270.039

10925A-38R-6, 38-39

687.42

S. ciperoensis

LO

top NP23

29.1710.027

10925A-38R-7, 15-16

688.69S. akropodus

HO

NP23

29.2940.046

9925A-39R-2, 82-83

691.76

S. avisLO

NP23

30.5120.033

1925A-44R-2, 55-56

730.09

Table 1: Main Sphenolithus events for Gulf of Mexico (ages direct from our Leg 154 research). 1error is age of next sample. 2reliability index isnumber occurrences in top or bottom 10 samples (boldface = 2 researchers). 3revised measured composite depth (meters). NOTE: internal researchon Leg 154 down to 30.679Ma

80

Bergen et al.

D)+!HC HT!=

9Q43>P=A!C) LDBCB.?R=<HWW!C)K

F?HC."")!%"<=A!C)
L+:B.?R=<HWW!C)K)T<!C.<!BC
HC%W)

2

2

P

P

6580QO>PU!+<"FH=) L@:H+=K

HA!.HW
WH<)?HW .R.W)
A?BT!DHW .R.W)

U!+<"

Figure 2: Sphenolith morphologic terms. U = upper, L = lower

the HO of S. ciperoensis up to the LO of medium-sizedbU DZ *0 % D@#m) Discoaster druggii, is coincident with
the Oligocene-Miocene boundary and dated at 23.030Ma
in Leg 154. The total range of S. belemnos is used to define
the limits of Zone NN3 herein, as the HO of Triquetrorhabdulus carinatus (base NN3) is diachronous within the
Gulf of Mexico. The LO of S. heteromorphus may be used
to subdivide Zone NN3, as it is the marker for the base ofZone CN3 of Okada & Bukry (1980). The base of Zone
NN6, defined by the HO of S. heteromorphus, represents
the extinction of conical sphenoliths with monocrystalline
spines. Only four significant datum’s recognized herein(Table 1) occur after extinction of S. heteromorphus, allof which are placed in proximity to the base of the Middle
Pliocene.
4. Systematic Paleontology
Size variation through time is an iterative process welldemonstrated by the genus Sphenolithus. The axiom forsize is that the larger variants have shorter stratigraphic
ranges within the range of the species. In this study, eighttaxa proved to have stratigraphically significant size variants, one of which is described herein as a new species.
Sphenolithus microdelphix is separated as a new species
GROUP NAMEELEMENT SIZE

APICAL SPINE TYPE

hemisphericalmediumcompound5

abies

conicalmediumcompound4

2B

dissimilis

cylindroconicalmediumcompound

2C1

belemnosconicalmediummonocrystalline

narrow2

2C2

calyculus

conicalmediummonocrystalline

equant3

2C3

delphix

conicalmediummonocrystalline

flared3

2C4

heteromorphus

conicalmediummonocrystalline

broad

3

capricornutus

biconical (flaring)

mediumcompound4

umbrellus

sphaeroconicallargevariable

5

ciperoensis

lanceolate

small

duocrystalline

1

moriformis

2A

PERIPHERAL OUTLINECONICAL

Grp. No.

because of its relevance to the recognition of the Oligocene-Miocene boundary. Size variants among existing
species include S. celsus - S. predistentus. Size categories
follow those defined by Young et al. (1997).
Morphologic terms used herein are shown in Figure 2.
Aubry (2014) provided an excellent synopsis of the genus;
her five main morphologic groupings are followed hereinwith the exception of her elongate group, replaced herewith a sphaeroconical group (Table 2). Aubry (2014) also
distinguished two basic types of apical spines (ortholithid
and heliolithid) important to her recognition of groups
and subgroups. Instead, three basic types of apical spines
are recognized herein, following Young et al. (1997):(1) compound; (2) monocrystalline; and (3) duocrystalline. Ilselithina fusa is considered because it is morphologically similar to the sphaeroconical group with which it
shares having large proximal elements (i.e. a small numberof elements per cycle). Forty-two sphenolith taxa are considered; about half of these taxa are classified as conical(Group 2), which is divided into six subgroups (Table 2).
Drawings of the taxa belonging to Groups 1–4 are shownin Figure 3 and with their ranges in Figures 4 and 5. Thesedrawings were rendered from light photomicrographs;
they were based on holotypes, when possible.
PROXIMAL CYCLE

No. Taxa

5

2
3rounded3
12

Table 2: Morphologic groupings of Oligocene-Pliocene Sphenolithus. The bold type-face and shading emphasize important morphologicalcharacteristics that separate groupingsOligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

S. belemnos group (2C1)

S. moriformis group (1)S. neoabies

S. bipedis
sp. nov.

81

S. moriformis

S. puniceus
sp. nov.

S. grandis

S. belemnos (long spine)

S. abies group (2A)
S. belemnos (short spine)

S. abies

S. verensis

S. delphix group (2C3)

S. apoxis sp. nov.

S. pseudoradians

S. dissimilis group (2B)Long

S. tintinnabulum

Base Length

Short

Long

S. truaxii
sp. nov.

Stem Length

S. microdelphix sp. nov.

S. procerus

Short

S. delphix

S. dissimilis

S. spinula sp. nov.

S. disbelemnos

S. calyculus group (2C2)

S. calyculus

S. conicus

S. heteromorphus group (2C4)

S. preasii sp. nov.

S. capricornutus group (3)S. cometa

S. paratintinnabulum
sp. nov.

S. multispinatus
S. capricornutus

S. heteromorphus

S. pseudoheteromorphus

S. umbrellus group (4)S. umbrellus

S. avisS. milanetti

Figure 3: Schematics of Sphenolithus taxa for morphologic Groups 1-4

4.1 Sphenolithus moriformis group
This group is defined by their hemispherical lateral outlines. The five species included in this group are differentiated by their size, birefringence, and proximal cycle
morphology (Table 3).
Sphenolithus neoabies Bukry & Bramlette, 1969
Pl. 1, figs 1–4

1969 Sphenolithus neoabies, Bukry & Bramlette, p. 140,
pl. 3, figs. 9–11.
Remarks: Bukry & Bramlette (1969) noted the small
size of the species (2–4#m). The flared proximal cycle ofthe holotype is also considered diagnostic, which resultsin height to width ratios of less than 1 (holotype: 0.71).
The indented proximal surface appears linear in crosspolarized light (XPL).

82

Bergen et al.

NN12

5.5
Messinian

6.0
6.5
7.0

3.607

3.666 (GoM HO)

CN11b

CN10a

S. abies

CN10b

S. moriformis & abies groups

3.909 (Leg 154
HO; GoM acme)

CN11a

NN14 CN10c
NN13

5.333

3.531

S. verensis

NN15

3.531

S. moriformis

MIDDLE

5.0

NN16 CN12a

S. neoabies

4.5

3.600

EARLY

4.0

PLIOCENE

3.5

Zanclean

3.0

Piacenzian

Zone
Age Epoch/
Okada
Martini & Bukry(Ma) Stage (1971) (1980)

NN11b CN9b

7.246

7.5
NN11a CN9a

LATE

8.0
8.5

CN8b
NN10

Tortonian

9.0
9.5
10.0

CN7b
NN9

10.5

CN7a

11.0

NN7

CN5b

NN6

CN5a

13.706NN5CN4Langhian

14.5

13.429

13.82

15.0

15.498
15.97

16.0

NN4

16.5

CN3

18.0
18.5

EARLY

17.5

Burdigalian

17.0

NN3

CN2

NN2

CN1c

15.93819.0
19.5

LO in NP19

20.0

Figure 4: Range diagram of Sphenolithus moriformis (1) and S. abies (2A) morphologic groups

HRO-16.517

17.347LO in NP11

17.425(GoM HO)17.517

S. bipedis sp. nov.

15.5

S. apoxis sp. nov.

14.0

MIDDLE

13.0
13.5

CN6

S. puniceus sp. nov.

12.5

Serravallian

12.0

NN8
11.63

MIOCENE

11.5

CN8a

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

83

Occurrence: Sphenolithus neoabies ranges from lower
Middle Miocene (NN4) to basal Middle Pliocene (NN16).
The HO of S. neoabies, along with that of S. moriformis,
represent the extinction of the genus in the GoM. This
event is dated in Leg 154 research at 3.531Ma (Table 1).
The LO of S. neoabies is also well-constrained in the Leg
154 research, placed in Sample 925C-38-3, 135–136cm
and dated at 15.938Ma (0.020Ma error).

illustrated by Bramlette & Wilcoxon (1967). Sphenolithus
moriformis is distinguished from S. puniceus sp. nov. by
being less birefringent. Haq & Berggren (1978) distinguished S. grandis from S. moriformis by its larger size
and more disjoined elements.
Occurrence: S. moriformis is the last surviving speciesof Sphenolithus in the GoM and its earliest Middle Pliocene
extinction has been calibrated in Leg 154 (Table 1).

Sphenolithus bipedis Bergen & de Kaenel, sp. nov.
Pl. 1, figs 5–12
Derivation of name: from Latin bi, meaning two andpedis, meaning foot.
Diagnosis: Hemispherical sphenolith with a flared
proximal cycle and arcuate proximal surface.
Description: Very small to medium hemisphericalsphenolith having a compound apical spine. Proximal
cycle is laterally-extended or “flared”, resulting in height
to width ratios of less than 1 (0.81–0.91 for five measured specimens). Proximal surface strongly concave andarcuate. Size: 2.8–6.4#m (holotype: Length [L] = 2.4#m;
width [W] = 2.8#m).
Remarks: S. neoabies is a younger and generally
smaller version of S. bipedis. Their stratigraphic ranges are
separated by approximately 1.58 million years in the ODP
Leg 154 materials. The proximal surface of S. bipedis is
more arcuate than the more linear and less concave proximal surface of S. neoabies. Other hemispherical sphenoliths do not possess a flared proximal cycle. S. bipedis has
been referred to as “S. delphix (no stem)” in the BP GoM
lexicon.
Holotype: Pl. 1, figs 5–6
Type locality: ODP Leg 154, Hole 929A, Ceará Rise,
western equatorial Atlantic
Type level: Sample 35-3, 125–27cm (23.155Ma),
Zone NP26, Upper Oligocene
Occurrence: In Leg 154, the LO of S. bipedis wasplaced in Sample 925A-38R3, 70–71cm within Zone
NP24 and dated at 28.971Ma (error 0.041Ma), but it ispossible the species could range down into Zone NP23.
In Leg 154, the HO is well-constrained within lower Zone
NN4 in Sample 928B-28-2, 115–116cm and dated at
17.517Ma (0.022Ma error).

Sphenolithus puniceus Bergen & de Kaenel, sp. nov.
Pl. 1, figs 19–26
Derivation of name: from Latin puniceus, meaning
purplish-red.
Diagnosis: A highly birefringent (first order blue to
red interference colors) hemispherical sphenolith.
Description: Medium to large, hemispherical sphenolith with a compound apical spine. The species is distinguished by its very high birefringence - exhibiting firstorder blue to red interference colors at its core in bothplan and lateral view. Height to width ratio = 0.94–1.08
on three measured specimens. Size (six specimens): 6.8–
11.2#m (holotype: L = 8.6#m; W = 8.0#m).
Remarks: S. moriformis and S. grandis also havehemispherical lateral outlines and compound apicalspines, but do not display high first order blue to red birefringence.
Holotype: Pl. 1, figs 21–22
Type locality: ODP Leg 154, Hole 926B, Ceará Rise,
western equatorial Atlantic
Type level: Sample 42-4, 35–37cm (20.350Ma), Zone
NN2, Lower Miocene
Occurrence: This species occurs from the Upper
Eocene (NP19) through Middle Miocene (NN4), but is far
less abundant than the morphologically-similar S. moriformis. In Leg 154, the HO of S. puniceus is in Sample
925C-37-4, 30–32cm (15.498Ma, 0.020Ma error) andits HRO in Sample 925A-9-5, 130–131cm (16.517Ma,
0.020Ma error). In the GoM, the observed HO is coincident in age to the HRO in Leg 154.

Sphenolithus moriformis (Brönnimann & Stradner,
1960) Bramlette & Wilcoxon, 1967
Pl. 1, figs 13–18
1960 Nannoturbella moriformis Brönnimann & Stradner(pro parte), p. 368, figs. 11–13, 16, non figs. 14–15.
1967 Sphenolithus moriformis (Brönnimann & Stradner)
Bramlette & Wilcoxon (pro parte), p. 124, pl. 3, figs. 1–4,
non figs. 5–6.
Remarks: The Lower Eocene holotype has a hemispherical lateral outline, whereas the conical specimen illustrated by Brönnimann & Stradner (1960) is not included
within this species concept; neither is the conical specimen

Sphenolithus grandis Haq & Berggren, 1978
Pl. 1, figs 27–30
1978 Sphenolithus grandis Haq & Berggren, p. 1192,
pl. 3, figs. 17–20.
Remarks: The original authors distinguished S. grandis from
S. moriformis by its large size (10–18#m) and elements disjoined throughout most of their length. Typically, it exhibits
first order yellow to orange birefringence colors. Specimens
as small as 8.5#m (the holotype) have been observed.
Occurrence: We have been unable to establish areliable stratigraphic range for this species. In Leg 154,
S. grandis occurs persistently in samples down into lower
Zone NN6 and a single specimen was observed in upper
Zone NN5. In the GoM, the HO was determined to bein middle Zone NN11. Perch-Nielsen (1985) showed adashed range of Zones NN7-NN11 for this species.

84

Okada
Martini & Bukry(1971) (1980)

16.04016.477

16.5

NN4

17.5
18.0
18.5

17.51717.60917.872

EARLY

19.5

16.859NN3 CN2

MIOCENE

19.0

CN3

Burdigalian

17.0

HO-13.408 Ma

19.33119.552

20.0

NN1

23.03

CN1b

23.5

NP26

24.0

19.392

CN1a

S. calyculus

22.5
23.0

18.852 (GoM)

21.36223.093

S. delphix

22.0

21.302

S. microdelphix sp. nov.

21.5

NN2 CN1c

S. spinula sp. nov.

Aquitanian

21.0

18.070inc @20.291

20.44

20.5

S. heteromorphus

15.97

S. pseudoheteromorphus

16.0

Zone

S. preasii
sp. nov.

Epoch/
Stage

S. milanetti

Age
(Ma)

Bergen et al.

acme @
23.25324.5
24.73127.5
28.0

NP24 CP19a
28.1

28.5

29.5
30.0

28.570?

EARLY
Rupelian

29.0

S. conicus

27.0

25.097

S. bipedis sp. nov.

26.5

OLIGOCENE

26.0

LATE
Chattian

NP25 CP19b

25.5

24.68324.664

S. conicus (<7)

25.0

28.971?

NP23 CP18

28.971

S. heteromorphus group (with S. milanetti)

Figure 5: Range diagram of Sphenolithus dissimilis (2B), S. heteromorphus (2C), and S. capricornutus (3) morphologic groups

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

85

Zone

Okada
& Bukry Martini(1980) (1971)

Epoch/
Stage

Age
(Ma)
16.0

15.97

16.5

17.791
LRO18.086

CN2

NN3

18.5

EARLY

S. dissimilis

18.768

18.0

19.0
19.5
20.0

20.44

CN1c NN2

21.74020.5
21.0

Aquitanian

21.041

HRO19.832

18.768

S. disbelemnos

19.39218.612

S. paratintinnabulum sp. nov.

18.61217.5

MIOCENE

17.587

S. cometa

21.5
22.0
22.5

S. capricornutus

22.998

LRO22.757

22.978?
23.27422.65823.27424.281

NN1

23.03

23.0

CN1b

23.5

NP26

24.0

CN1a

S. procerus

24.5
25.0
25.5

OLIGOCENE

LATE

S. truaxii sp. nov.

Chattian

CP19b NP25

26.0
26.5
27.0
27.5

27.808CP19a NP24
28.1

28.0

S. capricornutus
group

S. dissimilis group
LO in NP17

CP18 NP23

EARLY

28.5

Rupelian19.41417.752

S. multispinatus

S. belemnos (short)

S. tintinnabulum

17.683

S. belemnos (long)

17.49517.60917.0

Burdigalian

CN3

NN4

29.0
29.5
30.0

86

Bergen et al.

4.2A Sphenolithus abies group
This group is represented by conical sphenoliths withcompound apical spines; the four species included are differentiated by their spine and proximal cycle morphologies (Table 3).
Sphenolithus verensis Backman, 1978
Pl. 2, figs 1–4
1978 Sphenolithus verensis Backman, p. 111, pl. 2,
figs. 4–6, 11, 12.
Remarks: S. verensis is retained for conical forms withcompound apical spines and flared proximal elements.
Occurrence: We have been unable to establish a reliable stratigraphic range for S. verensis in the GoM. In Leg
154, its range has been established as Middle Miocene(NN5) through Middle Pliocene (NN16). The LO is placedin Sample 926A-29-2, 141–143cm (13.429Ma; 0.022Ma
error) and the HO in Sample 926C-11H-4, 141–142cm(3.607Ma; 0.019Ma error).
Sphenolithus abies Deflandre in Deflandre & Fert,
1954
Pl. 2, figs 5–10
1954 Sphenolithus abies, Deflandre in Deflandre & Fert,
p. 41, pl. 10, figs. 1–4.
1967 Sphenolithus moriformis (Brönnimann & Stradner)
Bramlette & Wilcoxon (pro parte), p. 124, pl. 3, figs. 5–6,
non 1–4.
Remarks: Both of the specimens illustrated by light photographs by Deflandre (in Deflandre & Fert, 1954) areconical sphenoliths. Measurements of these two specimens
and the three Upper Miocene specimens illustrated hereinindicate that S. abies has a relatively shorter spine (heightspine to base ratio: 0.26–0.70) and larger lateral element
cycles (height upper to lower quadrant ratio measured in
XPL: 0.82–0.99) than the older Sphenolithus apoxis n.sp.
Occurrence: In Leg 154, the LO of S. abies was placed
within the Middle Miocene (NN5) in Sample 926A-29-6,
94–96cm (13.706Ma, 0.009Ma error); this event is not
SPECIES

GRP

SHAPE

PROXIMAL

OTHER DIAGNOSTICFEATURES

neoabies1

hemisphericalflaredflat base; younger thanbipedisbipedis1

hemisphericalflaredarcuate base; older than
neoabies

moriformis

1hemisphericalpuniceus

1

hemispherical

grandis1

hemisphericalverensis

2A

conicalabies

2A

conicalshorter spine; younger
than apoxis

apoxis2A

conicallonger spine; older thanabies

pseudoradians

2A

conicalspine: thick medial suture

blue-red birefringencecolorslarge elements; > 8μm
flaredTable 3: Sphenolithus Identification Table (Groups 1 & 2A). Representative species for each group are bold-faced

utilized in the GoM. Its HO represents the extinction of thegenus in the Leg 154 research, dated at 3.510Ma (Table 1).
However, the HO of the species in the GoM is immediately below those of S. moriformis and S. neoabies andbelieved to correspond to its HFO dated at 3.666Ma in the
Leg 154 research (Table 1). The top acme appears coincident between the GoM and the Leg 154 research, observedin Sample 926C-12H-3, 70–71cm and dated at 3.909Ma(0.016Ma error) in the latter. The HO of larger specimens(> 6#m) is placed in Sample 926A-12H-3, 73–74cm anddated at 3.707Ma (0.020Ma error) in the Leg 154 research;
this event is older in the GoM, correlated to the aforementioned top acme of the species in the Leg 154 research.
Sphenolithus apoxis Bergen & de Kaenel, sp. nov.
Pl. 2, figs 11–20
1960 Nannoturbella moriformis Brönnimann & Stradner(pro parte), p. 368, figs. 14–15, non figs. 11–13, 16.
1971 Sphenolithus dissimilis Bukry & Percival (proparte), p. 140, pl. 6, fig. 8, non figs. 7 & 9.
1997 Sphenolithus dissimilis Bukry & Percival 1971;
Maiorano & Monechi, pl. 1, figs. 9–10.
Derivation of name: from Greek apoxis, meaning tapering off.
Diagnosis: Paleogene to Early Miocene conical sphenolith with a compound apical spine.
Description: Small to large, elongate conical sphenolith with a compound apical spine. The apical spine exhibits a sweeping extinction upon rotation; its termination isrounded. The three cited specimens and five illustrated
herein have height to width ratios of 1.16–1.35; the relatively long apical spine (height spine to base ratio 0.75–0.91) and reduced lateral element cycles (height upper tolower quadrant ratio measured in XPL (0.30–0.75) are considered diagnostic). Size: 4.0–8.4#m (holotype: L = 6.0#m;
W = 4.8#m).
Remarks: Sphenolithus apoxis has been illustrated
under S. moriformis and S. dissimilis; the confusion with
S. dissimilis is caused by a specimen illustrated (fig. 8)
alongside the holotype (fig. 7) by Bukry and Percival(1971). Sphenolithus dissimilis has “shoulders”, which are
created by its cylindro-conical shape and the width differences between its base and spine. Sphenolithus apoxis
has uniform taper (i.e. conical shape) and is not shouldered. Sphenolithus apoxis has a longer spine and reduced
upper basal quadrants (lateral cycle elements) relative to
S. abies. The two species do not co-occur and their stratigraphic ranges are separated by an estimated 3.7 million
years in the Leg 154 research. Sphenolithus apoxis has
been referred to as “S. cf. procerus (tapered)” in the BP
GoM lexicon.
Holotype: Pl. 2, figs 15–16
Type locality: ODP Leg 154, Hole 929A, Ceará Rise,
western equatorial Atlantic
Type level: Sample 35–3, 125–127cm (23.155Ma),
Zone NP26, Upper OligoceneOligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

Occurrence: This species ranges from the Lower
Eocene (NP11) to Lower Miocene (NN4). In Leg 154,
the HO of S. apoxis is dated at 17.347Ma and its HFOat 17.425Ma (Table 1). In the GoM, the observed HO
is coincident in age to the HFO in Leg 154. The HOof larger variants (> 8#m) of S. apoxis may serve asa proxy for the HO of S. pseudoradians near the terminal Lower Oligocene and within Zone NP24; both
extinctions have been dated at 28.092Ma in Leg 154(see Table 1).
Sphenolithus pseudoradians Bramlette & Wilcoxon,
1967
Pl. 2, figs 27–30
1967 Sphenolithus pseudoradians Bramlette & Wilcoxon,p. 126,. pl. 2, figs. 12–14.
Remarks: This species is easily distinguished byapparent thickening along the median axis of its apicalspine.
Occurrence: Upper Eocene (NP18) to Lower Oligocene (NP24). The HO of S. pseudoradians has been dated
at 28.092Ma in the Leg 154 research (Table 1) and is amarker in the GoM.
4.2B Sphenolithus dissimilis Group
Sphenoliths with bases that are either cylindrical orslightly conical (minimal taper distally) are placed within
this group (Table 4). In specimens with high bases, theextinction lines cross and then parallel the lateral periphery (S. dissimilis, S. disbelemnos); if their bases are low,
the extinction lines cross and continue to diverge (S. procerus, S. paratintinnabulum). All five species includedin this group have compound apical spines. Sphenolithus
cometa is closely related to members of this group (S. procerus and S. dissimilis), but is placed within the biconicalGroup 3 because of its narrowly divergent spine. Two new
species are described, Sphenolithus truaxii and Sphenolithus paratintinnabulum.
Sphenolithus truaxii Bergen & de Kaenel, sp. nov.
Pl. 2, figs 21–26
Derivation of name: named in honor of GoM foraminifera specialist and native Louisianan, Stephen Truax III(retired BP).
Diagnosis: Cylindrical sphenolith whose lateral element cycle creates a distinct central bulge.

87

Description: Small to medium, elongate (length towidth ratios 1.3–2.0), cylindrical sphenolith. The moderate to long spine is compound (sweeping extinction), but
is less than or equal to the height of the base (height spine
to base ratio 0.74–1.0). The lateral cycle (upper basal)
is wider than both the spine and proximal cycle (lower
basal); the height of the lateral cycle is less than or equal
to the height of the proximal cycle. When oriented 45°
to the polarizer, the linear extinction lines are oriented
diagonally and their intersection orthogonal. Length: 4.6–
6.8#m. (holotype: L = 6.8#m; W = 3.4#m).
Remarks: Sphenolithus truaxii is unique in being
cylindrical and having a broad lateral cycle of elements,
which gives the impression of a central bulge. Whenspecimens are oriented 45° to the polarizer, the diagonal
extinction cross appears linear and their intersection forms
a 90° angle. Sphenolithus truaxii has been referred to as“S. decussatus” in the BP GoM lexicon.
Holotype: Pl. 2, figs 21–23
Type locality: ODP Leg 154, Hole 929A, Ceará Rise,
western equatorial Atlantic
Type level: Sample 35-3, 125–127cm (23.155Ma),
Zone NP26, Upper Oligocene
Occurrence: middle Eocene (NP17) through Lower
Miocene (upper NN3). Its HO in Leg 154 was documented
in Sample 928B-28-6, 40–41cm (17.791Ma, 0.021Ma error).
Sphenolithus procerus Maiorano & Monechi, 1997
Pl. 3, figs 1–6
1997 Sphenolithus procerus, Maiorano & Monechi,
p. 103, pl. 1, figs. 1–3.
1998 Sphenolithus dissimilis Bukry & Percival 1971;
Young (pro parte), pl. 8.6, fig. 10, non fig. 9.
Remarks: Sphenolithus procerus is distinguished from
S. dissimilis by its longer apical spine (length spine tobase ratio > 1.0). Because of its shorter base, the extinctionlines of S. procerus cross and are strongly divergent when
specimens are oriented 45° to the polarizer. S. procerus
also tends to have a broader spine than S. dissimilis (widthof spine to base ratio > 0.50).
Occurrence: The HO of S. procerus is a GoM marker
dated at 18.612Ma in the Leg 154 research (Table 1). The
LO of S. procerus extends down near the base of the Upper
Oligocene (Zone NP24) in GoM and Leg 154. In Leg
154, the LO is placed in Sample 926B-63X-6, 66–67cm(27.808Ma; 0.046Ma error).

SPECIES

GRP

L/W

Up/Lo Quads

UPPER QUADS

truaxii

2B>=

bulgedLOWER QUADSSpine/BaseSpine Length≤

mediumOTHER DIAGNOSTIC FEATURE(S)procerus

2B>=

equant>long

extinction cross & diverge

dissimilis

2B

>

<

narrow<long

extinction cross & parallel

disbelemnos

2B

>

<

<<

v.shortheight > widthparatintinnabulum

2B

=

≤

<<

v.shortbase height = width

extinction “X”

Table 4: Sphenolithus Identification Table (Group 2B): cylindroconical. Representative species is bold-faced. L/W is a length/width ratio; Up/Lo
Quads is a size ratio; Spine/Base is a length ratio

88

Bergen et al.

Sphenolithus dissimilis Bukry & Percival, 1971
Pl. 3, figs 7–10
1971 Sphenolithus dissimilis Bukry & Percival (proparte), p. 140–141, pl. 6, figs. 7, 9; non pl. 6, fig. 8.
non 1997 Sphenolithus dissimilis Bukry & Percival
1971; Maiorano & Monechi, pl. 1, figs. 9–10.
non 1998 Sphenolithus dissimilis Bukry & Percival
1971; Young, pl. 8.6, figs. 9–10.
Remarks: Bukry & Percival (1971) illustrated two XPL
photomicrographs of S. dissimilis. The holotype has a“shouldered” appearance caused by the width difference between the spine and base, both of which are subcylindrical; the other specimen tapers uniformly and has
a rounded distal termination. This other specimen (pl. 6,
fig. 8) is considered here a different species (S. apoxis).
Inclusion of these clearly conical forms in S. dissimilis is
unwarranted.
Sphenolithus dissimilis is distinguished from S. procerus by its shorter apical spine (length spine to base,i*G0 W D\Za\ "LOi)+L 0K G*+ HGIHL, hi+L^ *HL Lf*G1O*G01
lines of S. dissimilis cross and become nearly parallel
when specimens are oriented 45° to the polarizer (Pl. 3,
fig. 8). Sphenolithus dissimilis also tends to have a narrower spine than S. procerus (width spine to base ratio
W Z\@Za\ ")F,e / :L,OG'iE bD<>Da +*,L++LN *HL NGKKL,L1OL
in width between the three-part apical spine and widerbase of S. dissimilis, in addition to the difference in birefringence between the lower (proximal cycle) and upper(lateral cycle) portions of the base. This contrast in optical birefringence, observed when specimens are oriented
45° to the polarizer, is most obvious in cylindroconicalsphenoliths (Group 2B) and the Sphenolithus belemnos
subgroup 2C1.
Occurrence: The HO of S. dissimilis and the HO of
S. disbelemnos are markers for a Lower Miocene horizonin the GoM, both dated at 18.768Ma in Leg 154 research(Table 1). The LO of S. dissimilis is lowermost Miocene (NN2) in the GoM and Leg 154, dated at 22.658Ma(Table 1).
Sphenolithus disbelemnos Fornaciari & Rio, 1996
Pl. 3, figs 11–28
1996 Sphenolithus disbelemnos Fornaciari & Rio,
p. 28, pl. 2, figs. 7–10; pl. 3, 19–20; pl. 4, figs. 1–4.
1996 Sphenolithus aubryae de Kaenel & Villa, p.128,
pl. 11, figs. 16–18.
Remarks: Sphenolithus aubryae and S. disbelemnos canbe differentiated by size, using a practical length of 4#m
based on their holotypes (Pl. 3, figs. 17–20). It would be
expected that the smaller S. disbelemnos would have thelonger stratigraphic range of the two species. However, thetwo species are considered synonymous herein because
they were not differentiated in either the GoM or Leg 154
research. Sphenolithus disbelemnos has priority. Sphenolithus disbelemnos is more elongate (height to width ratios> 1.35) than S. paratintinnabulum.

Occurrence: The HO of S. dissimilis and the HO of
S. disbelemnos are markers for a Lower Miocene horizonin the GoM, both dated at 18.768Ma in Leg 154 (Table 1).
Sphenolithus disbelemnos has a distinct acme (HCO andLCO) in both GoM and Leg 154 within the lowermost Miocene (NN2), spanning approximately 220 kyr (Table 1).
The LO of S. disbelemnos extends into the terminal Oligocene (NP26) in the GoM, the GSSP in northern Italy(9.4m below base Neogene), and Leg 154 (Sample 926B51-3, 30–31cm; 23.274Ma; 0.019Ma error). In Leg 154,
the LRO of the species within the basal Miocene (NN2)in Sample 928B-36-6, 100–102cm (22.757Ma; 0.020Ma
error) is far more reliable than the LO of the species (single, isolated occurrence).
Sphenolithus paratintinnabulum Bergen & de
Kaenel, sp. nov.
Pl. 3, figs 29–30; Pl. 4, figs 1–6
Derivation of name: from Greek para, meaning beside,
near, or by, and from Latin tintinnabulum, meaning small
bell.
Diagnosis: Equant cylindrical sphenolith with a very
short compound spine.
Description: Small to medium, roughly cylindricalsphenolith. The height to width ratio of the base is equantto nearly equant (1.0–1.1). The compound conical spine
is very short (spine to specimen length ratio 0.25–0.50).
When oriented 45° to the polarizer, the lateral cycle displays a 1st order white birefringence, while the proximal
cycle is faintly birefringent. At 0° in XPL, the upper quadrant (lateral cycle) appears shorter than the lower quadrant(proximal cycle). L = 2.2–3.6#m; W = 1.8–2.8#m (holotype: 2.8#m x 2.4#m). Length to width ratios of specimens
1.14–1.29. Ten specimens measured, including the four
illustrated herein.
Remarks: Sphenolithus paratintinnabulum is distinguished from S. tintinnabulum by its roughly cylindricalshape, as the conical S. tintinnabulum is strongly tapered
and triangular in lateral view.
Holotype: Pl. 4, figs 1–2Type locality: ODP Leg 154, Hole 926B, Ceará Rise,
western equatorial Atlantic
Type level: Sample 48-3, 30–32cm (22.208Ma), Zone
NN2, Lower Miocene
Occurrence: The HO of S. paratintinnabulum isa useful Lower Miocene marker in the GoM, dated at
18.612Ma in Leg 154 (Table 1). The LO of S. paratintinnabulum extends into the terminal Oligocene (NP26) in
the GoM and Leg 154, dated at 23.274Ma (Sample 926B51-3, 30–31cm; 0.019Ma error).
4.2C Sphenolithus heteromorphus Group
Conical sphenoliths having apical spines that extinguish
optically as a single unit (monocrystalline) are includedin this group of ten species. Four subgroups are recognized on the morphology of the proximal element cycle

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus(i.e. lower quadrants) as they appear at 0# '& '$- *&!%(.,-( ".(-)'.&+ (Table 5). Taxa within each subgroup are
distinguished by spine length and symmetry, as well as
overall size.
4.2C.1 Sphenolithus belemnos subgroup(narrow proximal cycle)
The S. belemnos subgroup is distinguished by their narrow(height > width) lower quadrants of the proximal cycle,
as they appear in XPL with specimens oriented N-S. In
this orientation, the upper basal quadrants (lateral cycle)
appear reduced relative to the lower basal quadrants (proximal cycle).
Sphenolithus tintinnabulum Maiorano & Monechi,
1997
Pl. 4, figs 7–18
1997 Sphenolithus tintinnabulum Maiorano & Monechi,
p. 104, pl. 1, figs. 4–6.
Remarks: Maiorano & Monechi (1997) diagnosed
S. tintinnabulum as triangular in outline and having a very
short apical spine. Their two XPL photomicrographs of a
specimen show that the apical spine is monocrystalline.
The two specimens in Maiorano & Monechi (1997) andthree illustrated herein (Pl. 4, figs 7–9, 11–14) have apical spines whose length is less than 1/2 the total lengthof the specimen (holotype ~ 1/3). Such typical specimensof S. tintinnabulum are distinguished from S. belemnos
by having shorter apical spines. Specimens identified asS. tintinnabulum with longer spines (Plate 4, figures 15–18),
up to 2/3 the total length, are distinguished from S. belemnos by their flared proximal cycles and more delicate
spines. Sphenolithus tintinnabulum differs from S. paratintinnabulum by its triangular outline.
Occurrence: The stratigraphic range of S. tintinnabulum in the Leg 154 material is from Sample 926B-44-5,
90–91cm(21.041Ma;0.020Maerror)toSample928B-28-3,
145–146cm (17.609Ma; 0.022Ma error), encompassing
Zones NN2 to NN4. The longer stemmed variants havebeen observed throughout Zone NN3 in Leg 154, but have
not yet been fully investigated.
SPECIES

SUB
GRP

LOWER
QUADS

SPINE
LENGTHOTHER DIAGNOSTICFEATURE(S)tintinnabulum

2C1

narrowshort

belemnos

2C1

narrow

long

calyculus

2C2

equantlongequant quadrants

conicus2C2equantmediumtriangular outline

preasii

2C2equantmediumshouldered outline

spinula

2C3

flaredshort

microdelphix

2C3

flared

long

> 8μm

delphix

2C3

flared

long

≤ 8μm

pseudoheteromorphus

2C4

broad

long

stem asymmetricheteromorphus

2C4

broad

long

triangular baseTable 5: Sphenolithus Identification Table (Group 2C): monocrystalline
spines. Representative species for each subgrouping are bold-faced

89

Sphenolithus belemnos Bramlette & Wilcoxon 1967
Pl. 4, figs 19–30
1967 Sphenolithus belemnos Bramlette & Wilcoxon,p. 118, pl. 2, figs. 1–3.
Remarks: Bramlette & Wilcoxon (1967) illustrated two
specimens of S. belemnos in the same three light photomicrographs; they designated the upper specimen as theholotype. The holotype has a relatively longer apical spine(0.70 total specimen length) than the lower specimen(spine 0.60 total specimen length). More detailed examination of S. belemnos in the Leg 154 materials has shownstratigraphic potential in dividing this species into variants
with relatively shorter (Pl. 4, figs 19–26) and longer (Pl. 4,
figs 27–30) apical spines; this subdivision is currently
placed where the apical spine is 2/3 of the total specimen
length.
Sphenolithus belemnos is distinguished from typicalS. tintinnabulum by their longer apical spines. In specimens with similar spine lengths, S. tintinnabulum is distinguished from S. belemnos by its flared base and moredelicate apical spine.
Occurrence: The total range of S. belemnos defines
Zone NN3, which is delineated in the Leg 154 data by
variants with shorter apical spines. The LO of S. belemnos is utilized as a marker in the GoM and dated at
19.414Ma in Leg 154 (Table 1). The HO of the species in
the GoM has been observed in less than 10% of wells andwas previously interpreted as reworked; this event is dated
at 17.683Ma (Table 1) and confirmed by two researchers in the Leg 154 materials. The HRO of S. belemnos in
the GoM is a more reliable event, expressed as a top in
more than 90% of wells examined; this event is dated at
17.831Ma in the Leg 154 research (Table 1).
4.2C.2 Sphenolithus calyculus subgroup(equant proximal cycle)
The S. calyculus subgroup is distinguished by the equant(height = width) lower quadrants of the proximal cycle.
The three taxa in this group, roughly separated by thelengths of their monocrystalline apical spines, are better
distinguished by their peripheral outlines and basal quadrant dimensions (Table 5). Sphenolithus preasii sp. nov. isdescribed as new.
Sphenolithus calyculus Bukry, 1985
Pl. 5, figs 1–6
1985 Sphenolithus calyculus Bukry, p. 600, pl. 1,
figs. 13–19.
Remarks: We have measured eight specimens, including
the holotype. Bukry (1985) mentioned that the height ofupper and lower basal quadrants is the same when specimens are oriented at 0°; this has been confirmed and isconsidered diagnostic. Our measurements have demonstrated that the height of the base is equal to or slightly lessthan the width of the base (ratio 0.8–1.0). Bukry (1985)
also described the spine being equal to or taller than the

90Bergen et al.

base and this ratio varies from 1.0 to 2.5. The length of thespecies is revised to include specimens between 4.0 and9.5#m in length, from the size of 5–9#m given by Bukry(1985).
Occurrence: The HO of S. calyculus is just above
the base of Zone NN3, dated as 19.331Ma in Leg 154(Table 1). Its LO is upper Oligocene (NP25) in both the
GoM and Leg 154, where it is placed in Sample 926B-55-1,
80–81cm and dated at 24.683Ma (0.017Ma error).
Sphenolithus conicus Bukry, 1971
Pl. 5, figs 7–18
1971 Sphenolithus conicus Bukry, p. 320, pl. 5,
figs. 10–12.
Remarks: Bukry (1971a) described S. conicus as triangularin lateral view, suggesting it has uniform taper and a pointed
apical spine. He distinguished it from S. heteromorphus byhaving a greater portion of base to spine (ratio > 1.0). Sphenolithus conicus and S. preasii sp. nov. have similar spine tobase ratios, but S. conicus has a triangular outline (straightlateral periphery), convex indented proximal surface, andrelatively taller upper quadrants (height upper to lower
quadrant ratio > 0.80). Sphenolithus apoxis sp. nov. has acompound apical spine (sweeping extinction).
Bukry (1971a) restricted S. conicus to 7–12#m inlength, but specimens as small as 4.4#m have been
observed. It is much more difficult to discriminate smaller
specimens of S. conicus because their common size andlower birefringence (1st order white) with other sphenoliths, especially in the high diversity assemblages near theend of its range in lower Zone NN4.
Occurrence: In Leg 154, S. conicus ranges from theupper Lower Oligocene (NP24) through Lower Miocene(NN4), reliably dated from 28.971Ma (Sample 925A38R-3, 70–71cm; 0.041Ma error) to 17.609Ma (Sample
928B-28-3, 145–146cm; 0.022Ma error). The species also
ranges down into the upper Lower Oligocene (NP 24) inthe GoM, immediately above the HO of S. pseudoradians.
The HO of S. conicus has long been utilized by BP as a
GoM marker, but this event is associated with the top of
the larger (> 7um) and more birefringent (1st order yellow to orange interference colors) specimens. The HO oflarge S. conicus in the GoM has been calibrated to its first
downhole abundance increase in the Leg 154 research,
dated at 20.291Ma (Table 1). The top acme of S. conicus
is a deep-water GoM marker horizon in the terminal Oligocene (NP26) and is dated at 23.253Ma in the Leg 154
research (Table 1).
Sphenolithus preasii Bergen & de Kaenel, sp. nov.
Pl. 5, figs 19–30
Derivation of name: named in honor of geologist Patrick
Preas of ALS-Ellington, Houston.
Diagnosis: Conical sphenolith with a monocrystalline
apical spine, a “shouldered” lateral profile, and arcuate
proximal surface.

Description: Medium to large, conical sphenolith.
The monocrystalline apical spine is moderate to long(~ 1/2 to 3/4 the total length of the specimen), has apointed to rounded apex, and becomes extinct when thespecimen is aligned with the polarizing direction. In thisorientation, the four basal quadrants each appear equantand the height of the upper quadrants is less than theheight of the lower quadrants (0.67–0.76 ratio). In lateral profile, the proximal surface is concave and arcuate.
The basal lateral periphery appears “bulged”, giving theimpression of shoulders when contrasted to the width of
the spine at its juncture with the base (most evident at
45° in XPL). L = 5.6–10.0#m; W = 4.0–6.4#m (holotype:
9.8#m x 6.4#m).
Remarks: Sphenolithus preasii is somewhat transitional between S. conicus and S. milanetti. It differs from
S. conicus by its “bulged” basal lateral periphery, arcuate
proximal surface, and relatively lower upper quadrants
bHLGIH* )..L, *0 E0gL, -)iN,i1* ,i*G0 % Z\=a\ Sphenolithus milanetti also has a “bulged” base, but its base ishemispherical and constructed of much larger elements.
The basal upper quadrants (lateral cycle) of S. milanetti
is much more reduced than in S. preasii (both height
and width) relative to the size of their lower quadrants(proximal cycle). Sphenolithus preasii is also similar to
S. heteromorphus, but the latter species is not shouldered(uniform taper), has a linearly indented proximal surface,
and the height of its upper (lateral cycle) and lower (proximal cycle) quadrants are equal. The lower quadrant elements (proximal cycle) of S. heteromorphus appear broad(width > height), whereas those of S. preasii are equant.
Sphenolithus preasii has been referred to as “S. milanetti(elongate).” in the BP GoM lexicon.
Holotype: Pl. 5, figs 28–30
Type locality: ODP Leg 154, Hole 925C, Ceará Rise,
western equatorial Atlantic
Type level: Sample 38-6, 40–41cm (16.097Ma), Zone
NN4, Lower Miocene
Occurrence: Sphenolithus preasii is rarely found insamples from the GoM. In Leg 154, this late Early Miocene species ranges from Sample 926B-35-3, 75–76cm(upper NN3) to Sample 925C-38-5, 95–96cm (middle
NN4), which are dated from 17.872Ma (0.018Ma error) to
16.040Ma (0.022Ma error). The LO of larger specimens(>9#m) of S. preasii is in Sample 928B-28-4, 95–96cm in
the Leg 154 research, dated at 17.672Ma (0.011Ma error).
4.2C.3 Sphenolithus delphix subgroup(flared proximal cycle)
The S. delphix subgroup is distinguished by its flared
proximal cycle. Bukry (1973) referred to S. delphix as
tri-radiate because of its long apical spine and laterally-extended proximal cycle. The three taxa in this groupare distinguished by spine length and size (Table 5). Two
new taxa are described in this subgroup, S. spinula andS. microdelphix.

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

Sphenolithus spinula Bergen & de Kaenel, sp. nov.
Pl. 6, figs 1–8
Derivation of name: from Latin spinula, diminutive ofspina, meaning spine.
Diagnosis: Tri-radiate sphenolith with a short monocrystalline spine.
Description: Small to medium conical sphenolith.
Specimens are triangular in profile, where length is equal
to or slightly less than the width (ratio 0.85–1.0). The
monocrystalline apical spine becomes extinct when specimens are aligned with the polarizer. The spine is short,approximately 1/2 of the total length of the specimen(spine to specimen length ration is 0.46–0.57), and has apointed distal termination. At 0° to the polarizer, the upperbasal quadrants appear shorter than the lower quadrants(1/2 to 3/4 height ratio). The proximal cycle elements
flare laterally, where proximal cycle width approximately
1.5–2.0 times the width of the lateral cycle. The proximal
surface is concave. L = 2.2–5.4#m; W = 2.6–5.4#m (holotype: 5.2#m x 5.2#m).
Remarks: This taxon differs from both S. delphix andS. microdelphix by its shorter apical spine. Sphenolithus
bipedis sp. nov. and S. neoabies have flared proximal
cycles, but are hemispherical forms with compound apicalspines. Sphenolithus spinula sp. nov. is distinguished fromS. tintinnabulum by its flared proximal elements characteristic of the S. delphix subgroup. It tends to be larger andh,0iNL, bEL1I*H % gGN*Ha *Hi1 S. tintinnabulum, but there
is significant overlap in the size and dimensions of these
two species. Sphenolithus spinula has been referred to as“S. delphix (stumpy)” in the BP GoM lexicon.
Holotype: Pl. 6, figs 1–3
Type locality: ODP Leg 154, Hole 926B, Ceará Rise,
western equatorial Atlantic
Type level: Sample 50-5, 140–142cm (23.072Ma),
Zone NP26, upper Oligocene
Occurrence: Sphenolithus spinula ranges fromthe Upper Oligocene (NP25) to lowermost Miocene(NN2) in the GoM and Leg 154. It is dated in the Leg
154 research from 25.097Ma (Sample 925A-26-5, 125–126cm; 0.027Ma error) to 21.302Ma (Sample 926B-45-4,
45–46cm; 0.028Ma error).
Sphenolithus microdelphix Bergen & de Kaenel,
sp. nov.
Pl. 6, figs 9–20
Derivation of name: from Greek mikros, meaning small
and delphix, meaning tripod.
Diagnosis: small to medium, tri-radiate sphenolithwith a long monocrystalline spine.
Description: Small to medium conical sphenolith. Specimens are tri-radiate in profile, where length isequal to or greater than the width (ratio 1.0–1.75). The
monocrystalline apical spine is greater than 2/3 of the total
length of the specimen. Its becomes extinct when specimens are aligned with the polarizer. In this orientation,91

the upper basal quadrants (lateral cycle) appear equal toor less than the height of the lower quadrants (proximal
cycle). The base of the proximal cycle elements flare laterally and proximally; their width is 1.5–2.0 times the widthof the lateral cycle. The proximal surface is concave.
Specimen length is less than 8#m. Length of ten measured
specimens: 2.4–6.4#m; width measured specimens: 2.4–
5.2#m (holotype: 5.2#m x 5.0#m).
Remarks: Sphenolithus microdelphix differs from
S. delphix by being smaller and from S. spinula by its longer apical spine. This taxon has been referred to as “S. cf.
delphix (small)” in the BP GoM lexicon.
Holotype: Pl. 6, figs 11–13
Type locality: ODP Leg 154, Hole 929A, Ceará Rise,
western equatorial Atlantic
Type level: Sample 35-3, 125–27cm (23.155Ma),
Zone NP26, upper Oligocene
Occurrence: Sphenolithus microdelphix ranges from
Upper Oligocene (NP25) through lowermost Miocene(NN2). The HO of S. microdelphix is a marker in the
GoM, dated at 21.362Ma in Leg 154 (Table 1). The LO
is dated at 24.731Ma (928B-41-5, 140–141cm; 0.028Ma
error) in Leg 154.
Sphenolithus delphix Bukry, 1973
Pl. 6, figs 21–25
1973 Sphenolithus delphix Bukry, p. 679, pl. 3,
figs. 19–22.
Remarks: Bukry (1973) gave the length of S. delphix as
8–12#m and that criterion is followed herein. It is distinguished from S. microdelphix sp. nov. by its size and fromS. spinula sp. nov. by its size and longer spine.
Occurrence: Sphenolithus delphix is restricted to theuppermost Oligocene (upper NP25-NP26). Its stratigraphic
range is coeval between the GoM and Leg 154. The HO of
S. delphix is a GoM marker and dated at 23.093Ma in Leg
154 (Table 1); its HO is positioned 3.5 meters below thebase Neogene in the GSSP section in northern Italy. In Leg
154, the LO was seen in Sample 926B-55-1, 25–26cm,
dated at 24.664Ma (0.019Ma error).
4.2C.4 Sphenolithus heteromorphus
subgroup (broad proximal cycle)
The S. heteromorphus subgroup is distinguished by its
broad lower quadrants (proximal cycle). Only two taxa
are considered in this subgroup, S. heteromorphus andS. pseudoheteromorphus (Table 5).
Sphenolithus pseudoheteromorphus Fornaciari &Agnini, 2009
Pl. 7, figs 1–5
2009 Sphenolithus pseudoheteromorphus Fornaciari &Agnini, p. 97, pl. 1, figs. 1–16; pl. 2, figs. 1–5, 9, 13.
Remarks: This species is well illustrated in Fornaciari &Agnini (2009). The asymmetry of its monocrystalline apical spine is considered diagnostic.

92

Bergen et al.

Occurrence: Fornaciari & Agnini (2009) reported
the range of this species within NN2. We have observed
this species in the GoM and Leg 154, but its stratigraphic
range is not well constrained. In Leg 154, S. pseudoheteromorphus has been observed intermittently in lower Zone
NN3 from Sample 926C-39-5, 110–112cm (19.392Ma;
0.022Ma error) to Sample 926B-35-6, 140–141cm(18.070Ma; 0.017Ma error).
Sphenolithus heteromorphus Deflandre, 1953
Pl. 7, figs 6–13
1953 Sphenolithus heteromorphus Deflandre, p. 1786,
p. 1, figs. 1–2.
Remarks: Deflandre (1953) published a light photomicrograph of a single specimen. This holotype and thefour specimens illustrated herein share the following
properties: (1) the apical spine is higher than the base:(2) the height of the upper and lower quadrants (lateraland proximal cycles) appear equal when specimens arealigned with the polarizer; and (3) the height to width
ratio of the proximal element cycle is less than 1/2.
Length is highly variable; specimens as small as 4.0#m
have been observed.
Occurrence: The HO of S. heteromorphus marks the
top of Zone NN5 (13.408Ma). Four S. heteromorphus
events are utilized in the GoM Basin by BP, all of whichhave ages established in Leg 154 (Table 1). Three of these
events appear coeval between the GoM and Leg 154. The
17.791Ma age for the LO of S. heteromorphus establishedin Leg 154 (Table 1) is younger than that observed in the
GoM. In many deep-water GoM wells, the LO of S. heteromorphus has been associated with the HO of Discoaster
saundersii, dated at 18.852Ma in our Leg 154 research(Sample 926B-38-3, 15–17cm; 0.020Ma error).
4.3 Sphenolithus capricornutus group
The S. capricornutus group is characterized by their flared(i.e., distally divergent) apical spines (Table 6), resulting
in a biconical shape.
Sphenolithus multispinatus Maiorano & Monechi,
1997
Pl. 7, figs 14–17
1997 Sphenolithus multispinatus Maiorano & Monechi,
p. 104, pl. 1, figs. 14–16.

Remarks: Six specimens were measured, including thetwo original specimens of Maiorano & Monechi (1997).
The angle between the divergent apical spines ranges from
42–56° and specimen length between 3–6#m. Maiorano& Monechi (1997) stated a length of “about 6–7#m” forthe species. Sphenolithus multispinatus has a more divergent spine than S. cometa, but less divergent spine thanS. capricornutus. Damaged specimens of S. multispinatus
with single or no spines can be confused with S. calyculus- these two species have similar bases.
Occurrence: Maiorano & Monechi (1997) gave arange of upper Zone NN3 to lower Zone NN4 for S. multispinatus at DSDP Site 563 in the North Atlantic. Its HO
is in lower Zone NN4 for both the GoM and Leg 154,
observed in Sample 928B-28-2, 80–82cm and dated at
17.495Ma (0.031Ma error). The LRO in Leg 154 is inupper Zone NN3 in Sample 926B-35-7, 32–33cm anddated at 18.086Ma (0.026Ma error). The species occurs
very sporadically in Leg 154 samples down into Zone
NN2 (Sample 926C-40-6, 60–62cm; 19.792Ma). Single specimens were also observed in Sample 926B-44-3,
85–86cm (20.950Ma; NN2) and Sample 926B-50-4,
40–41cm (22.978Ma; NN1).
Sphenolithus cometa de Kaenel & Villa, 1996
Pl. 7, figs 18–25
1996 Sphenolithus cometa de Kaenel & Villa, p. 128,
pl. 11, figs. 22–24.
Remarks: For S. cometa, the narrow divergence of its
branched spine (~ 10–36°) distinguishes it from S. capricornutus and S. multispinatus. Sphenolithus cometa
can be more difficult to distinguish from S. dissimilis andS. procerus, which are other “shouldered” forms with long,sub-cylindrical, compound apical spines, though the distal
spine of those two species is not branched. L = 3.6–7.0#m.
Occurrence: The HRO of S. cometa has been used in the
GoM, for which an age of 19.832Ma has been established in
Leg 154 (Table 1). In Leg 154, it ranges from middle Zone
NN2 to lower Zone NN4. The stratigraphic range of thespecies is very reliable in Leg 154, where it is dated from21.740Ma (926B-46-7, 5–6cm; 0.025Ma error) to 17.587Ma(Sample 928B-28-3, 110–112cm; 0.024Ma error).
Sphenolithus capricornutus Bukry & Percival, 1971
Pl. 7, figs 26–30

SPECIES

GRP

L/W

Up/Lo Quads

LOWER QUADSSpine/BaseSpine Length

cometa3>≤variable>long

OTHER DIAGNOSTIC FEATURE(S)multispinatus

3

>

≤

variable=longwide divergence

capricornutus

3

≥

≤

broad

>

mediumwide divergencemilanetti

4

>

<<

hemisph.

≤mediummonocrystalline spine

avis

4

=

-

hemisph.

<<

short

duocrystalline spine

umbrellus

4=-hemisph.

-none

no spinenarrow divergence

Table 6: Sphenolithus Identification Table (Groups 3 & 4): biconical and sphaeroconical. Representative species for each group are bold-faced. L/W
is a length/width ratio; Up/Lo Quads is a size ratio; Spine/Base is a length ratioOligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

1971 Sphenolithus capricornutus Bukry & Percival,
p. 140, pl. 6, figs. 4–6.
Remarks: Seven specimens were measured, including
the two original specimens of Bukry & Percival (1971).
The angle between the divergent apical spines ranges from
54–76°. Bukry & Percival (1971) gave a size range of
6–10#m, but specimens as small as 4.8#m in length havebeen observed. Sphenolithus capricornutus has a moredivergent spine than S. cometa and S. multispinatus.
Occurrence: The HO of S. capricornutus approximates the top of the Oligocene in the GoM, Leg 154 andthe Italian GSSP. It actually ranges just into the basal Neogene in the GSSP section in northern Italy (0.4m above
base Neogene) and in Leg 154 (22.998Ma; Table 1). The
LO in Leg 154 is upper Oligocene (NP25), where it isdated at 24.281Ma (Table 1). In the Italian GSSP, it ispresent in the bottom sample studied (26.9 meters below
the base of the Neogene).
4.4 Sphenolithus umbrellus group
The S. umbrellus group has a sphaeroconical shape. The
three species included herein have hemispherical bases
constructed of very large, strongly arcuate elements. Species are distinguished by their apical spines (Table 6).
Sphenolithus milanetti Maiorano & Monechi, 1998
Pl. 8, figs 1–9
1998 Sphenolithus milanetti Maiorano & Monechi,
p. 249, pl. 2, figs. 30–31.
2016 Sphenolithus pospichalii Jiang, Wang, Varol,da Gama & Blaj, p. 61, pl. 1, figs. 1–8.
Remarks: Sphenolithus milanetti is distinguished by its
hemispherical proximal cycle constructed of large elements, short monocrystalline spine, and reduced lateralcycle elements. Maiorano & Monechi (1998) mentionedthat the proximal cycle elements (lower basal quadrants)
are about twice as large as the lateral cycle elements (upperbasal quadrants); our measurements of six specimens confirm this observation both in the height (0.29–0.47) andwidth (0.43–0.58) ratios of the small upper to larger lower
quadrants. The spine is approximately half the length of
the specimen, but may be reduced to 1/3 the total length(Plate 8, figs. 7–9). Maiorano & Monechi (1998) gave asize range of 6–10#m for the species.
This species differs from S. umbrellus by having aspine and from S. avis by having lateral elements and a
monocrystalline spine. Both S. umbrellus and S. avis are
Oligocene species. Sphenolithus milanetti may actually
be more closely related to other Miocene sphenoliths withmonocrystalline spines, all of which have conical shapes.
In fact, S. preasii sp. nov. seems the most likely ancestor
to S. milanetti (Figure 5).
Sphenolithus pospichalii is considered here a juniorsynonym, as its dimension ratios are nearly identical to
S. milanetti; both species are reported restricted to NN4
and given nearly identical size ranges. Specimens of

93

S. pospichalii illustrated by Jiang et al. (2016) are better
preserved than the holotype of S. milanetti.
Occurrence: Sphenolithus milanetti has been rare indeep-water GoM samples. It is restricted to Zone NN4in Leg 154, where it ranges from Sample 928A-26-2,
85–86cm (16.859Ma; 0.015Ma error) to Sample 925A-9-5,
50–51cm (16.477Ma; 0.021Ma error); its HRO occurs
in Sample 925A-9-6, 105–106cm (16.579Ma; 0.020Ma
error).
Sphenolithus avis Aljahdali, Wise, Bergen &Pospichal, 2015
Pl. 8, figs 10–24
2015 Sphenolithus avis Aljahdali, Wise, Bergen &Pospichal, p. 193, pl. 1, figs. 1–5; pl. 2, figs. 1–6.
Remarks: The diagnosis of S. avis by Aljahdali et al.
(2015) stressed its “short tapered apical spine and wide
flaring proximal basal elements that at the end taper proximally”. All light and electron photomicrographs of thespecies show a short tapered distal projection composedof two elements. The lanceolate sphenoliths also possess duocrystalline spines and are Paleogene, as is S. avis
(Figure 6). The short apical spine of S. avis is 1/3 to 2/3
the length of the specimen (versus less than 1/2). Length
to width ratio includes specimens slightly taller than wide
(ratio 0.9–1.2). Size range: 3.3–6.5#m.
The proximal elements of S. avis are very large andform a hemispherical shape, features which its shares with
S. umbrellus and S. milanetti; however, S. umbrellus has
no distal projection. Sphenolithus milanetti is a late Early
Miocene species with a monocrystalline, spine and prominent lateral elements. Sphenolithus avis is also smaller andhas a lower length to width ratio than S. milanetti. Thistaxon has been referred to as “S. proboscis” and “S. truaxii” in the BP GoM lexicon.
Occurrence: The HRO of S. avis in Leg 154(26.627Ma; Table 1) is coincident with the HO establishedin deep-water GoM wells over the past decade. The HO
of S. avis has since been placed within Zone NP25 in Leg
154 research and dated at 24.408Ma; the LO in the GoM
and Leg 154 is within Zone NP23 and tentatively dated at30.512Ma (Table1).
Sphenolithus umbrellus (Bukry, 1971) Aubry &Knüttel in Knüttel, 1986
Pl. 8, figs 25–30
1971 Catinaster? umbrellus Bukry, p. 50, pl. 3,
figs. 10–13.
1986 Sphenolithus umbrellus (Bukry, 1971) Aubry &Knüttel, in Knüttel, p. 279, pl. 5, figs. 1, 2, 5–10.
Remarks: Bukry (1971b) mentioned S. umbrellus has noknob or ornamentation and its simple construction of a single cycle of elements (no spine or lateral elements) makes
it unique among the genus Sphenolithus. Bukry (1971b)
gave a size range of 8–12#m for the species; measured
specimens from the two citations and our work range from

94

Bergen et al.
Zone

Age
(Ma)

Epoch/
Stage

24.0

Okada
Martini & Bukry(1971) (1980)

NP26 CN1a

24.21524.24824.304

HRO-24.365

24.5

S. ciperoensis group24.40824.62524.68324.70025.0

25.047

S. distentus

29.5
30.0

28.65528.57028.65529.171

NP23 CP18
LO in
NP23

LO in
NP23

LO in
NP22

LO in
NP23

LO in
NP23

LO in
NP23

LO in
NP16

S. akropodus

29.0

EARLY
Rupelian

28.5

S. predistentus

S. peartiae

S. avis26.926

S. tawfikii sp. nov.

NP24 CP19a
28.1

S. triangularis sp. nov.

28.0

HRO-26.627

S. directus sp. nov.

27.5

S. patifunditus sp. nov.

27.0

26.126

S. bulbulus sp. nov.

26.5

OLIGOCENE

26.0

S. ciperoensis

25.5

LATE
Chattian

NP25 CP19b

HRO
29.127

LO in
NP21

Figure 6: Range diagram of Sphenolithus ciperoensis (5) morphologic group

4.4–8.0#m high by 4.8–10.35#m wide. Height is equal toor less than its width (ratio 0.65–1.00) and its shape in
top view is circular to broadly elliptical. It is possible thatS. umbrellus may have originated from S. avis by developing a higher proximal cycle and the complete loss of anapical spine.
Occurrence: The HO of S. umbrellus has been
observed in the Upper Oligocene in six deep-water
GoM wells, where it has been associated with the HO of
S. ciperoensis (top Zone NP25). This is roughly coincident
to the HRO of S. umbrellus in the Leg 154 research, dated
at 24.233Ma (Sample 926B-53X-5, 110–11cm; 0.018Ma
error). The HO was observed stratigraphically higher near
the top of Zone NN1 in Sample 928B-37-1, 10–11cm anddated at 22.819Ma (0.021Ma error). The LO in Leg 154
is in Zone NP24, but is unreliable and placed in Sample
928B-48X-6, 3–4cm (27.890Ma; 0.040Ma error).
4.5 Sphenolithus ciperoensis group
These lanceolate sphenoliths appear smooth in XPL
because their spines are duocrystalline and their basal elements are small. It is assumed all taxa within this group
have delicate and long branched spines, whose branches
are not usually preserved. For this reason, length is measured on complete specimens from the proximal surface
to the point of maximum constriction below the flared
distal branch. Within this lanceolate group, taxonomic
separation is primarily based on the extinction patternwhen specimens are oriented 45° degrees to the polarizer.

The subgroupings are further divided based on extinction angle or orientation (Table 7). Extinction angles
can differ significantly between sides of the same specimen. Sphenolithus triangularis sp. nov. is distinguishedsolely on its equidimensional outline in lateral view. Half
the species included in this group are new or emended.
Drawings representing the extinction patterns and lateraloutlines of the twelve taxa in the S. ciperoensis groupare shown in Figure 7 and with their ranges (along with
S. avis) in Figure 6.
Sphenolithus ciperoensis Bramlette & Wilcoxon, 1967
Pl. 9, figs 1–8
1967 Sphenolithus ciperoensis Bramlette & Wilcoxon,p. 120, pl. 2, figs. 15–20.
Remarks: The length of the holotype for S. ciperoensis is about 6.3#m. Cross-polarized light micrographs ofthis specimen show extinction lines that touch at 0° to
the polarizer, but are separated and form obtuse extinction angles when oriented at 45°. The lateral periphery of
S. ciperoensis is straight, from which distinguishes it fromtwo new species described herein, S. patifunditus (concave peripheral surface on proximal cycle) and S. bulbulus(convex peripheral surface on proximal cycle).
Occurrence: The LO and HO of S. ciperoensis
define the base of Zone NP24 (CP19a) and top Zone
NP25 (CP19b), respectively. The stratigraphic ranges of
two sizes of S. ciperoensis are well-constrained in boththe GoM and Leg 154 (Table 1). Specimens greater thanOligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

SPECIESLENGTH/WIDTHLATERALPERIPHERY

ciperoensis>

linearpatifunditus>

concavetawfikii>

linearbulbulus>

convexdistentus>

linear-convex

akropodus>

concave

peartiae>

linearpredistentus>

linearcelsus>lineartribulosus>

lineardirectus>

lineartriangularis=

linearPROXIMAL
CYCLE

flaredEXTINCTION LINES
Angle

OTHER DIAGNOSTIC FEATURE(S)

Orientation

obtusediagonal

obtusediagonal

= 90

axial

~90

diagonal

ext. lines separate at 45°

acutediagonal

ext. lines touch at 45°

acutevariable

acutevariablefeet

0horizontal

smaller (≤ 9μm)

feet

0

horizontal

larger (> 9μm)

feet

0

horizontal

serrate spine0

diagonal

bulgedflared95

diagonalaligned main axes

equidimensional

Table 7: Sphenolithus Identification Table (Group 5): lanceolate. Representative species is bold-faced

6#m, akin to the size of the holotype, have a shorter stratigraphic range than smaller specimens. The base of Zone
NP24 is delineated on the LO of S. ciperoensis - confirmedby two researchers in our Leg 154 materials – and dated
at 29.171Ma. Specimens at the base of its range are verysmall, less than 3μm. Older appearances for S. ciperoensis reported in published literature are assumed to include
broader taxonomic concepts, such as S. bulbulus sp. nov.
(eg. Raffi et al., 2016). The top of Zone NP25 represents
the extinction of lanceolate sphenoliths and is dated herein
at 24.215Ma (Table 1). The first downhole increase in
S. ciperoensis has stratigraphic utility in the GoM andhas been tied to the HCO of the species in the Leg 154
research dated at 24.456Ma (Table 1).
Sphenolithus patifunditus Bergen & de Kaenel,
sp. nov.
Pl. 9, figs 9–16
Derivation of name: from Latin pateo, meaning lie open
and funditus, meaning entirely, totally, completely.
Diagnosis: An elongate lanceolate sphenolith witha flared base and concave peripheral surfaces along its
length.
Description: Small, elongate, conical sphenolith. In
lateral view, specimens appear smooth in XPL, as is typical of lanceolate sphenoliths. At 0° to the polarizer, thespine is faintly birefringent and bisected by a longitudinal
suture; the base is brightly birefringent (1st order white)
and its two extinction lines touch along the longitudinalaxis. At 45° to the polarizer, the entire specimen exhibits
a 1st order white birefringence. The paired extinction lines
remain separate in this orientation, their individual extinction angles are obtuse or nearly obtuse (80–120°), and theextinction lines are oriented diagonally. The base is flaredwith a concave peripheral surface. L = 4.4–4.9#m; W =2.8–3.0#m (holotype 4.8#m x 2.8#m).
Remarks: Sphenolithus patifunditus is distinguishedfrom all other lanceolate sphenoliths by its flared baseand concave peripheral surfaces, along with its obtuse

extinction angles. Sphenolithus ciperoensis has straightlateral peripheries. Sphenolithus akropodus is an Early Oligocene species with a flared base, but its extinction angles
are acute. Sphenolithus patifunditus has been referred to as“S. ciperoensis (flared)” in the BP GoM lexicon.
Holotype: Pl. 9, figs 11–12
Type locality: ODP Leg 149, Hole 899B, easternequatorial Atlantic
Type level: Sample 9-6, 15–16cm, Zone NP25, Upper
Oligocene
Occurrence: The HO of S. patifunditus is much
more reliable than the LO in both the GoM and Leg 154.
The HO is in Sample 926B-54X-1, 60–61cm dated at
24.304Ma (0.023Ma error) in Leg 154, with specimens
observed in 8 of 10 samples at the top of its range. The LO
was observed in Sample 928B-50X-2, 5–6cm and dated at
28.655Ma (0.028Ma error) in Leg 154 by two researchers, but observed in only 2 of 10 samples at the base of
its range. The LO was calibrated in only two deep-water
GoM wells.
Sphenolithus tawfikii Bergen & de Kaenel, sp. nov.
Pl. 9, figs 17–20
Derivation of name: Named in honor of Egyptian nannofossil biostratigrapher Essam Tawfik.
Diagnosis: A lanceolate sphenolith whose paired
extinction lines are oriented parallel to the main axes andhave orthogonal extinction angles.
Description: Medium-sized, elongate, conical sphenolith. In lateral view, specimens appear smooth in XPL,
as is typical of lanceolate sphenoliths. At 0° to the polarizer, the spine is faintly birefringent and the extinctionlines of the brightly birefringent (1st order white) blocky
basal elements touch or nearly touch. At 45° to the polarizer, the entire specimen exhibits a 1st order white birefringence. The paired extinction lines remain separate
in this orientation, their individual extinction angles are
orthogonal, and the extinction lines are oriented parallelto the main axes of the sphenolith. The spine may have aBergen et al.

S. ciperoensis

S. patifunditus
sp. nov.

ObtuseExtinction Angle Decreasing

96

Type level: Sample 23-3, 80–81cm, Zone NP25,
Upper Oligocene
Occurrence: The HO of S. tawfikii is used as a marker
in the GoM, where it is paired with the HO of Helicosphaera bramlettei. The HO of S. tawfikii is coeval in Leg
154, where it is dated at 25.047Ma (Table 1). Its LO has
been documented in the middle Lower Oligocene in the
GoM (mid NP23), but below the reach of our Leg 154
research (30.679Ma).

longitudinal suture and be branched. L = 5.6–6.0#m; W =3.2–3.6#m (two specimens).
Remarks: The orthogonal extinction angles, combined with the alignment of the extinction lines with themain axes of the sphenolith, are diagnostic for S. tawfikii.
Sphenolithus tawfikii has been referred to as “S. cathetus”
in the BP GoM lexicon.
Holotype: Pl. 9, figs 19–20
Type locality: DSDP Leg 101, Hole 628A, western
Atlantic

Sphenolithus bulbulus Bergen & de Kaenel, sp. nov.
Pl. 9, figs 25–30; Pl. 10, figs 1–6
Derivation of name: from Latin bulbulus (diminutive),meaning a swelling.
Diagnosis: An elongate lanceolate sphenolith with abulged, convex base (proximal cycle periphery) whose
extinction lines remain separate at 45° and have orthogonal extinction angles.
Description: Small to medium, elongate, lanceolate
sphenolith. In lateral view, specimens appear smoothin XPL, as is typical of lanceolate sphenoliths. At 0° to

S. tawfikiisp. nov.

S. distentus

S. peartiae

S. akropodus

S. peartiaeS. predistentus
S. celsus

S. tribulosus

Horizontal

S. bulbulus
sp. nov.

Intermediate

Figure 7: Schematics of Sphenolithus taxa within morphologic Group
5 (S. ciperoensis). Taxa are subdivided based on their extinction angle

Sphenolithus directus Bergen & de Kaenel, sp. nov.
Plate 9, figures 21–24
Derivation of name: from Latin directus, meaningstraight, direct, set in order.
Diagnosis: A lanceolate sphenolith with two linear toslightly curved extinction lines, each extending from thelateral to proximal peripheries.
Description: Small to medium, elongate, conical sphenolith. In lateral view, specimens appear smooth in XPL, as
is typical of lanceolate sphenoliths. At 0° to the polarizer, thespine is faintly birefringent and the extinction lines of thebrightly birefringent (1st order white) basal elements touch.
At 45° to the polarizer, the entire specimen exhibits a 1storder white birefringence. The paired extinction lines remain
separate in this orientation, each extending diagonally fromthe lower lateral periphery to middle proximal periphery,
forming a high angle to the horizontal. The extinction lines
are linear to somewhat curved (concave toward the peripheries). L = 3.2–5.2#m; W = 2.4–2.8#m (two specimens).
Remarks: The diagonal extinction lines of S. directus
are linear to slightly curving – unique among the lanceolate sphenoliths. S. directus has been referred to as “S. aff.
ciperoensis” in the BP GoM lexicon.
Holotype: Pl. 9, figs 23–24
Type locality: DSDP Leg 101, Hole 628A, western
Atlantic
Type level: Sample 23-5, 80–81cm, Zone NP25,
Upper Oligocene
Occurrence: The HO of S. directus was first established within Zone NP25 in the GoM; this event wasplaced in Sample 926B-54-6, 115–116cm in Leg 154 anddated at 24.625Ma (0.032Ma error). The LO was observedin Sample 928B-50X-1, 15–16cm and dated at 28.570Ma(0.042Ma error).

Angle Independent

S. directus sp. nov.

S. triangularis sp. nov.

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

the polarizer, the spine is faintly birefringent to dark andbisected by a longitudinal suture; the base is brightly birefringent (1st order white) and its two extinction lines touchor nearly touch along the longitudinal axis. At 45° to thepolarizer, the entire specimen exhibits a 1st order whitebirefringence. The paired extinction lines remain separate
in this orientation. The diagonal extinction lines are oriented symmetric about the horizontal axis and extinction
angles vary around orthogonal (80–110°). The base has aconvex lateral periphery (bulged). The proximal surface
is often concave. L = 4.4–6.4#m; W = 2.4–4.0#m; baseheight 1.6–2.8#m; height spine to base ratio 1.3–2.8 (14specimens).
Remarks: Sphenolithus bulbulus is distinguished byits bulged base and diagonal extinction lines, which at
45° remain separate and form roughly orthogonal extinction angles. In S. distentus, the extinction lines touch at
45° to the polarizer, extinction angles are lower, and thelateral periphery is typically straight. Sphenolithus ciperoensis has a straight lateral periphery and higher extinction angles. Sphenolithus bulbulus has been referred to as“S. distentus var.” in the BP GoM lexicon.
Holotype: Pl. 10, figs 3–4
Type locality: ODP Leg 149, Hole 900A, easternequatorial Atlantic
Type level: Sample 49-3, 113–114cm, Zone NP24,
Upper Oligocene
Occurrence: The HO of S. bulbulus is a GoM marker,
which is coeval to its HRO in Leg 154 (24.365Ma); S. bulbulus ranges higher in the Mediterranean (Italy and Egypt)and Leg 154 (Table 1). The LO is in lower Zone NP23,
below the reach of our Leg 154 research.
Sphenolithus distentus (Martini, 1965) Bramlette &Wilcoxon, 1967, Bergen & de Kaenel, emend.
Pl. 10, figs 7–14
1965 Furcatolithus distentus Martini, p. 407, pl. 35,
figs. 7–9.
1967 Sphenolithus distentus (Martini, 1965) Bramlette& Wilcoxon; p. 122, pl. 1, fig. 5, pl. 2, figs. 4–5.
1971 Sphenolithus distentus (Martini, 1965) Bramlette& Wilcoxon; Roth, Franz & Wise, p. 1103, pl. 2, figs. 1–9;
pl. 3, figs. 1–2; text-fig. 5.
1971 Sphenolithus distentus (Martini, 1965) Bramlette& Wilcoxon; Martini, pl. 3, figs. 11–12.
Emended description: An elongate, lanceolate sphenolith with diagonal extinction lines symmetric about thehorizontal axis; the extinction lines touch at the median(no white birefringence between their apices) when
specimens are oriented 45° to the polarizer. Extinction
angles in this orientation are moderately acute to orthogonal (35–90°) and the entire specimen brightly (1st orderwhite) birefringent. At 0°, the spine is weakly birefringent and the two bright basal element touch at themedian. The lateral outline is straight, but rare specimens
may have a convex basal periphery. The height of the97base is about 0.8–1.6#m. The long conical apical spine
may branch.
Remarks: The holotype designated by Martini (1965)
is incomplete, only a brightly birefringent apical spinewith long branches typical of the entire lanceolate group.
This is further complicated by an original description
focused on the long branches and mention of a Miocene
age for this specimen. Bramlette & Wilcoxon (1967)
recombined the species into Sphenolithus, realizing its
stratigraphic utility in the Oligocene and correcting theage of the type material. Although they did not emend
the species, Bramlette & Wilcoxon (1967) illustrated thefirst light photomicrographs of a complete specimen anddescribed a depressed base composed of 10–12 spines
attached to a slightly convex base on a large apical spine.
Roth et al. (1971) published 11 electron photomicrographsof S. distentus, mentioning a proximal shield composed of
10–14 elements. Of more practical help is their sketch of
S. distentus (text-fig. 5) showing diagonal extinction lines
symmetric across the horizontal axis and touching at themedian axis, with an acute extinction angle (40°). Martini(1971) used the HO of S. distentus to define the top of
NP24 in his Cenozoic zonation, which he accompaniedwith two light photomicrographs. Common features to all
the aforementioned light photomicrographs of complete
specimens, as well as the sketch, are diagonal extinctionlines symmetrical about the horizontal that touch at themedian. The light photomicrograph of Bramlette & Wilcoxon (1967) differs in having higher extinction angles
and a base with a convex basal periphery. The four specimens in Bramlette & Wilcoxon (1967) and Martini (1971)
have bases between 1.0–1.5#m high, as opposed to the
2–5#m mentioned by Roth et al. (1970).
Sphenolithus distentus is distinguished by its diagonal extinction lines which touch at 45° to the polarizer.
Sphenolithus bulbulus sp. nov. has a higher base, higher
extinction angles (80–110°), and diagonal extinction linesthat remain separate at 45°. Sphenolithus peartiae and
S. distentus have similar extinction angles and baseheights, but the extinction lines of S. peartiae remain separate at 45° and their orientation may be asymmetric about
the horizontal axis. Sphenolithus predistentus has a shorter
hi+L b% Z\>@#m) and horizontal extinction line marking
the base of the spine.
Occurrence: The HO of S. distentus defines the baseof Zone NP25 (CP19b) and the LO the base of Zone CP18,
which subdivides Zone NP23. Both events are GoM markers. The HO of S. distentus has been dated in Leg 154 at
26.126Ma (Table 1), whereas the LO in lower Zone NP23
is below the reach of our Leg 154 research.
Sphenolithus triangularis Bergen & de Kaenel,
sp. nov.
Pl. 10, figs 15–24
Derivation of name: from Latin triangulus, meaning having three angles.

98

Bergen et al.

Diagnosis: A triangular lanceolate sphenolith whose
height is equal to or slightly less than its width.
Description: Small to medium, roughly equidimensional, triangular sphenolith. Height of specimen is equal
to or slightly less than the width (ratio 0.8–1.0). In lateralview, specimens appear smooth in XPL, as is typical oflanceolate sphenoliths. At 0° to the polarizer, the spine
is faintly birefringent to dark and the extinction lines ofthe brightly birefringent (1st order white) basal elements
touch. At 45° to the polarizer, the entire specimen exhibits a 1st order white birefringence. The paired extinctionlines remain separate in this orientation, their individual
extinction angles variable (50–140°), even on the same
specimen. The extinction lines are oriented diagonally.
The short spine may have a longitudinal suture. The lateral
peripheries are linear and the proximal surface normallyindented. L = 2.0–4.4#m; W = 2.4–5.6#m (eight specimens).
Remarks: The equidimensional outline of S. triangularis distinguishes it from all other lanceolate sphenoliths.
Sphenolithus avis is the same size with nearly identicalheight to width dimensions and also has a short spine, but
has a convex basal periphery and large proximal elements.
The straight lateral periphery of S. triangularis distinguishes it from S. avis in poorly preserved assemblages.
Holotype: Pl. 10, figs 17–18
Type locality: Cipero coast, north end, Locality 10 of
Bolli (1957), south Trinidad
Type level: Sample JS20, Globorotalia opima opima
Zone, Lower Oligocene, Zone NP24
Occurrence: The HO of S. triangularis is used as
marker in the GoM, where it is paired with the HO of
S. ciperoensis (> 6#m). This event is also within Zone
NP25 in Leg 154, dated at 24.700Ma (Table 1). In the
GoM, the LO of the species falls in lower Zone NP23,
below the Leg 154 research (30.679Ma).
Sphenolithus akropodus de Kaenel & Villa, 1996
Pl. 10, figs 25–30; Pl. 11, figs 1–4
1996 Sphenolithus akropodus de Kaenel & Villa, p. 127,
pl. 11, figs. 1, 2, 4–11.
Remarks: Sphenolithus akropodus was thoroughly documented by de Kaenel & Villa (1996), including two specimens transferred between the SEM and LM. Its proximal
elements extend just outside the lateral periphery of thespine, which is diagnostic. Only S. patifunditus sp. nov.
shares this proximal lateral extension among the lanceolate sphenoliths, but its entire lateral periphery is concave.
In S. akropodus, the base of the apical spine is convex
and sometimes bulged. De Kaenel & Villa (1996) gavethe length of the species as 7–9#m, but we have observed
specimens as small as 5.8#m long. The extinction angle
varies from moderately acute to orthogonal (35–90°) and
its orientation relative to the horizontal is variable. Sphenolithus peartiae shares these two extinction properties,
but lacks the proximal lateral extinction. For S. akropodus,

longer specimens tend to have higher extinction angles
and length to width ratios, which may prove useful to theeventual recognition of a new taxon.
Occurrence: There is stratigraphic merit in separating the species into two size categories at 8#m length, as
their extinctions have utility in both the GoM and Leg 154,
bracketing the NP23/NP24 boundary (Table 1). The HRO
of S. akropodus is also a GoM marker, approximating the
top of Zone NP23 (Table 1). The LO of S. akropodus is inlower Zone NP21 in the GoM.
Sphenolithus peartiae Bown & Dunkley Jones, 2012,
Bergen & de Kaenel, emend.
Pl. 11, figs 5–14
2012 Sphenolithus peartiae Bown & Dunkley Jones,p. 34, pl. 11, figs. 39–44.
Emended description: small to medium, elongate, conical sphenolith. In lateral view, specimens appear smooth in
XPL, as is typical of lanceolate sphenoliths. At 0° to thepolarizer, the spine is faintly birefringent to dark and theextinction lines of the brightly birefringent (1st order white),wedged-shaped basal elements touch or nearly touch along
the longitudinal axis. At 45° to the polarizer, the entire specimen exhibits a 1st order white birefringence. The paired
extinction lines remain separate in this orientation, theirindividual extinction angles are moderately acute (40–75°),
and their orientation relative to the horizontal is symmetric or asymmetric (projecting proximally). The long spine
can display a longitudinal suture (best seen at 0°) and its
termination may be branched. The lateral peripheries arelinear and the proximal surface normally indented. L = 3.6–
8.2#m; W = 2.8–4.8#m. Height of base: 0.8–2.2#m; heightspine to base ratio 2.2–6.0 (27 specimens).
Remarks: Bown & Dunkley Jones (2012) described
S. peartiae with a “low base that meets the spine alonghorizontal or near horizontal sutures, but when 45°
to polarizing direction a birefringent structure passes
between the basal ‘feet’.” This description includes theholotype of S. predistentus and is not a means to differentiate the two species. A lot of the variation in the extinctionlines of the S. distentus - S. predistentus plexus is taken
up by S. peartiae. Sphenolithus predistentus is reserved
herein for specimens with horizontal extinction lines and,0)1NLN *0 1i,,0g gLNIL]+Hi.LN bLf*G1O*G01 i1IEL % CZ(aJKLL*7 i1N E0gL, hi+L+ b% Z\>@#m). Sphenolithus distentus is reserved herein for specimens with diagonal extinction lines symmetric to the horizontal, which touch when
specimens are oriented 45° to the polarizer. Sphenolithus
akropodus displays similar extinction angles and orientations to S. peartiae, but differs in the lateral extension ofits base. In S. bulbulus sp. nov., the base is bulged (convex
basal periphery). Sphenolithus peartiae has been referred
to as “S. predistentus var.” and “S. parviquetrus” in the BP
GoM lexicon.
Occurrence: There is stratigraphic utility in separating S. peartiae into two size categories at 7#m length,Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

as their extinctions fall on either side of the NP24/NP25
boundary in both the GoM and Leg 154 (Table 1). The LO
of S. peartiae is in mid Zone NP22 in the GoM.
Sphenolithus predistentus Bramlette & Wilcoxon,
1967
Pl. 11, figs 15–20
1967 Sphenolithus predistentus Bramlette & Wilcoxon,p. 126, pl. 1, fig. 6; pl. 2, figs. 10–11.
Remarks: The holotype of S. predistentus is illustrated
by two light photomicrographs of a specimen in XPL,
oriented at 0° and 45°. This specimen has an apicalspine that tapers to a point and is divided by a longitudinal suture. More importantly, Bramlette & Wilcoxon(1967) mention that the base of the apical spine is flat,
which on the holotype results in a horizontal extinction line separating the spine from two rounded “feet”.
These two feet are separated so that the extinction lines
extend downward (proximally) between them to forma point. In some specimens, the basal feet are wedgeshaped (Plate 11, figures 17–18). The extinction lines
are either horizontal at the base of the spine or havean extinction angle less than 20°. Height of base: 0.4–
0.74#m; height spine to base ratio: 7.3–9.9 (two citedspecimens and four herein). The horizontal extinction
at the base of the spine and rounded basal “feet” characterize S. predistentus, along with the larger S. celsus(i.e., specimens of S. predistentus > 9μm) and the serrate S. tribulosus. Sphenolithus predistentus grades into
S. peartiae (Pl. 11, fig. 16), which displays a higher
extinction angle (specimens oriented at 45°) and has ahigher base – resulting in lower spine to base ratios.
Occurrence: The HO of S. predistentus has long beenutilized as a marker in the GoM by all three BP heritage
companies, historically the next significant “top” belowthat of S. distentus (top NP24). This exceptionally reliable
event has been dated at 26.926Ma in our Leg 154 research(Table 1). The LO of S. predistentus is in Middle Eocene(NP16) in the GoM.
Sphenolithus tribulosus Roth, 1970
Pl. 11, figs 21–24
1970 Sphenolithus tribulosus Roth, p. 870, pl. 14, figs. 5,
7–8.
Remarks: The serrate apical spine of S. tribulosus is diagnostic and is clear on the holotype (electron photomicrograph). Its extinction pattern groups it with S. celsus andS. predistentus, which do not have serrate apical spines.
The light photomicrographs of the specimen illustrated by
Roth (1970) show the entire specimen a bright 1st orderwhite birefringence at 45° to the polarizer with a horizontal proximal surface below which are two separate,
rounded “feet”. At 0°, the spine of this specimen is weakly
birefringent and divided by a longitudinal suture. Roth(1970) stated the length of the holotype as 6.5#m, but it is
only 5.1#m long up to the base of the bifurcation.

99

Occurrence: S. tribulosus has not been differentiatedfrom S. predistentus in the GoM. In Leg 154, the HO has
been placed in Sample 925A-41R-CC, 12–13cm within
Zone NP23 and dated at 29.886Ma (0.036Ma error).
Perch-Nielsen (1985) showed the LO of this species in
NP21.
Sphenolithus celsus Haq, 1971
Pl. 11, figs 25–30
1971 Sphenolithus celsus Haq, p. 121, pl. 1, figs. 1–5;
pl. 5, fig. 4.
Remarks: Haq (1971) described a sphenolith with a large
stem protruding from a short base; the holotype (an electron photomicrograph) also has a branched apical spine
characteristic of the lanceolate group. The light photomicrographs of the two specimens illustrated by Haq (1971)
show a horizontal proximal surface below which are two
separate, rounded “feet” (i.e. small proximal cycle elements) and a spine divided longitudinally by a suture. Haq(1971) gave a size range of 10–18#m for the species, but0), 3Li+),L3L1*+ 0K HG+ *H,LL +.LOG3L1+ G1NGOi*L U <\Z#m
as a better definition (without branching). Specimens
less than 9.0#m are identified as S. predistentus. Length
to width ratio of cited specimens (four) and those herein(two) are 2.5–3.4.
Occurrence: S. celsus ranges from the Upper Eocene(NP19) to Lower Oligocene (near base of NP23) indeep-water GoM wells.
Genus Ilselithina Roth, 1970
Ilselithina fusa Roth, 1970
Pl. 6, figs 26–30
1970 Ilselithina fusa Roth, p. 856, pl. 7, figs. 2–3.
Remarks: Roth (1970) mentioned the lower number of
distal (6–10) and proximal shield (10–15) elements, aswell as antenna-like distal elements that are normallydamaged. The very small sizes of the holotype (2.4#m)and paratype (3.0#m) seem anomalous. Specimens
observed range from 3.2#m to 5.2#m. Ilselithina fusa has
a low number of proximal shield elements (i.e. large),a feature it shares with the sphaeroconical sphenoliths(S. umbrellus group). It differs from that group of sphenoliths by having an open central area and a flared distal
cycle of elements.
Occurrence: The range of I. fusa in the GoM is lowermost Oligocene (lower NP21) through lower Miocene(upper NN2). The HO is a GoM marker; in Leg 154, thisevent was placed in Sample 926B-40-6, 50–52cm anddated at 19.712Ma (0.024Ma error).
5. Depositories
The slides and samples are stored in the micropaleontologicalcollections of the Natural History Museum in Basel (NMB)
in Switzerland. Also curated at the NMB are the samplesof the foraminifera collections of H.M. Bolli (1957), whichhave been used to describe some of the new species herein.

100

Bergen et al.

Type material from DSDP and ODP cores are also stored
at the Bremen repository (Germany) and at College Station
repository (USA). ODP sample request numbers for Leg
154 are: 18687A (2003), 18687B (2005), 20484A (2005),
20484B (2006), 22364B (2011), 22433A (2011). Leg 154
nannofossil abundance data will be archived in the web database, PANGAEA (www.pangaea.de).
Acknowledgements
We are grateful to many people in BP GoM Exploration
for their support and encouragement over the years. We
thank Graham “Pinky” Vinson and Liz Jolley for permission to publish this manuscript. Special thanks areextended to Jim Newell, whose work for two of the BP
heritage companies contributed greatly to this work. Our
gratitude is extended to Drs. David Watkins and Richard
Howe for reviewing this manuscript.
References

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102

Bergen et al.

Plate 1
2!m

1

2

NN6

NN6

926A-27-4,146.5-148.5

S. neoabies

3

4

12

NP24

628A-23-5,80-81

S. bipedis
HOLOTYPE

22

S. puniceus

NN5

HOLOTYPE

925B-34-3,11-12

5

6

NP26

929A-35-3,125-127

13

14

NN9

926A-25-1,72-74

15

16

NN3

NN2

25

S. puniceus

926B-39-1,5-6

NP25

8

762B-17H-2

NN7

926A-26-4,112-114

S. puniceus

910628A-17-1,80-81

628A-23-5,80-81

17

NN4

18

928B-28-4,55-57

NN2

19

NN2

20

926B-41-3,135-137

S. puniceus
NN9

S. puniceus

925A-15-4,60-62

NP24

NN4

S. moriformis

NP25

26

NP24

S. bipedis

NN3

NN3

24

7

NN7

S. moriformis

23

NP25

S. bipedis

NN9

NN2

926B-42-4,35-37

NP26

S. bipedis

S. moriformis

21
HOLOTYPE

HOLOTYPE

S. neoabies
NP24

11

NN5

14.10!m

27 S. grandis 926A-25-1,72-74

NN6

29

10.50!m

NN6

NN6

28

8.80!m
926A-28-3,139.5-141.5

S. grandis

30

926A-28-3,139.5-141.5

S. grandis

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

103

Plate 22!m1

2
S. verensis

NN8

NN8

926B-25-6,36-38

NN8

3

4
S. verensis

NN1

11

13

926B-50-4,90-92

21
HOLOTYPE

22
S. truaxii

14

NP26

S. truaxii

HOLOTYPE

6
S. abies
HOLOTYPE

HOLOTYPE

Bo267

16

S. truaxii

926A-23-2,120-122

NP26

7

8
S. abies

NN11b

5.80!m
926B-19-2,61-62

17

929A-35-3,125-127

18

GoM,

S. apoxis

S. abies (>6)

6.40!m502-35-2, 110-111

NP24

NP24

20

JS20

S. apoxis (>8)
NP21

27

JS20

10

NN11b

19

NP24

29

NP24

26

9

NP25

NP24

S. truaxii

NN11b

NP25

NP26

25

926B-50-4,90-92

NN11b

NP26

S. apoxis

NN1

24

NN10

15

23

NP26

929A-35-3,125-127

5NN2

S. apoxis

S. apoxis
HOLOTYPE

926A-25-7,26.5-28.5

NN2

NN1

12

NN8

NN10

NP21

28

628A-29-2,80-81

S. pseudoradians

NP24

30

926B-64-5, 85-86

S. pseudoradians

104Bergen et al.

Plate 3Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

105

Plate 4
NN2

HOLOTYPE

2!m

1

NN2

HOLOTYPE

NN2

3

NN2

NN2

NN2

5

7

NN2

9
NN2

NN2

NN3
HOLOTYPE

3.00 !m2

926B-48-3,30-32

S. paratintinnabulum

4926B-49-1,140-141

S. paratintinnabulum

NN2

11

12

NN2

926B-48-3,30-32

S. tintinnabulum

22

S. belemnos

NN3

KR9397926B-48-3,30-32

S. paratintinnabulum
NN3

13

14

NN3

928B-28-5,110-111

S. tintinnabulum

NN3

21

6

24

S. belemnos

NN3926B-35-5,55-57

926B-48-3,30-32

S. tintinnabulum

NN3

15

16

NN3

3.90!m
926B-38-6,135-137

S. tintinnabulum

NN3

23

8

26

S. belemnos

top NN3

928B-28-4,117-118

S. tintinnabulum

NN3

17

18

NN3

928B-28-5,145-146

S. tintinnabulum

top NN325

10 Maiorano & Monechi, 1998
NN3

19

20

S. belemnos

NN3

27

28

S. belemnos

NN3926C-39-5,110-112

NN3KR9397

NN3

29

30

S. belemnos

NN3926B-37-1,105-107

106

Bergen et al.

Plate 5
+-A

)

(

P2+?

P2+?

N+N#DB?D+E&D?

'+ (/3"()3),

PPB

&

%

PPB

N+?:DBND&E-ABD-A-'+ (/3"()3),)()&

N+N#DB&DBE-+&D-+")%((

N+?:D&-D&EBBDB+N+O:E+OD&E-A&D-A?

(%'+ 0.$/,!!

N+O:E+ODAE&&D&"!

PP-

N+?:D&BDAENBDN+'+ (12!(),)#

N+?:D&BD?ENBDN-'+ 0.$/,!!

V;R;6l2Y'+ 0.$/,!!

(!

'+ 0.$/,!!

PPA

N+&!DBOD?EABDA-

*

)'

PP+

)!

N+?:DA&DBE-&D-"

PPA

('

'+ 0.$/,!!

PPA

(#

(*

N+N#DB&DBE-+&D-+")*'+ (12!(), G$"F

V;R;6l2Y

P2+?

PPA

PP+

PPA

N+&!DBOD?EABDA-

P2+?

'+ (12!(),)"'+ (12!(), G$"F

($
PPA

"

P2+&

PPA

(&

PP-

P2+&

)$

'+ (12!(), G$"F

PPB'+ 0.$/,!!

N+?:DBND&E-ABD-A-

P2+?

PPB

()

#

PPB

P2+?

P2+?

'+ (12!(),$'+ (/3"()3),

P2+?

))

PPB

N+&!DBOD?EABDA-

PPA

("
PPA

V;R;6l2Y&'

PPA

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

Plate 6107

108

Bergen et al.

Plate 7

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

109

Plate 8
2!m

NN4

1

NN4

4
NN4

2

5

3

925A-9-7,55-56

6

NP23

16

18

925A-9-7,55-56

21

S. avis925A-9-7,55-56

628A-25-1,80-81

12

24

926B-60-3,120-121

15

28

S. umbrellus
762B-17H-2

NP25

29

NP25

27

S. umbrellus

926B-60-3, 5-6

NP25

NP25

26

926B-59-3, 75-76

NP24

S. avis25

NP24

S. avis

14

NP25

NP24

23

NP24

NP24

S. avis

22

NP23

13

11

NP24

NP23

20

628A-25-1,80-81

9

NP24

NP24

NN4

S. milanetti

19

NP23

S. avis

8

NP23

NP23

17

NN4

NN4

S. milanetti

NP24

10

7
NN4

NN4

S. milanetti

NN4926B-56-6, 55-56

S. umbrellus

926B-56-4,15-16

NP25

30

S. umbrellus

628A-22-1,80-81

110

Bergen et al.

Plate 929.171 Ma
2!m1

29.171 Ma

2base NP24

base NP24

925A-38-7,15-16

S. ciperoensis
HOLOTYPE

12

S. patifunditus

22

4

NP24

900A-45-3,123-124

NP25

6

14

S. patifunditus
HOLOTYPE

NP25

HOLOTYPE

24

900A-43-5,94-95

900A-43-5,94-95

8

16

GoM

S. patifunditus

18

S. tawfikii
NP24

25
NP25

26

900A-43-5,94-95

910

S. patifunditus
NP24

HOLOTYPE

NP24

HOLOTYPE

GoM,

20

S. tawfikii28

900A-43-5,94-95

NP25

NP25

628A-23-3,80-81

NP25

29
NP24

S. bulbulus

NP25

19

27

JS20

NP25

NP24

NP24

S. bulbulus

NP25

17
NP24

NP25

628A-23-5,80-81

7

S. ciperoensis (>6)

15

23

S. directus

NP25

NP25

NP24

NP25

NP25

628A-23-5,80-81

5

S. ciperoensis

13899B-9-6,15-16

NP25

NP25

NP25

21

S. directus

3

S. ciperoensis

11
HOLOTYPE

NP24

900A-47-3,64-65

NP25

30

S. bulbulus

628A-21-3,80-81

Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus

111

Plate 10
NP25

2!m

1

3
NP25

2

NP24

HOLOTYPE

900A-43-5,94-95

S. bulbulus

5

4900A-49-3,113-114

NP24

11

12

S. distentus

13

900A-49-3,113-114

14

S. distentus

900A-49-3,113-114

22

24

HOLOTYPE

NP25

HOLOTYPE

926B-58-5,15-16

25

Egypt, Nile Delta

900A-49-3,113-114

26

Egypt, Nile Delta

NP23

19

18

JS20

S. triangularis

NP23

20

S. triangularis

Egypt, Nile Delta

NP23

27

GoM

10

S. distentus

NP24

NP24

29

NP23

S. akropodus (<8)

GoM

NP24

NP24

NP23

NP23

S. triangularis

8

S. distentus

17

NP23

23

926B-58-5,15-16

16

S. triangularis

S. distentus

NP24

NP25

15

NP25

S. triangularis

GoM

NP24

NP25

21

6

S. bulbulus

NP23

9

NP23

NP24

NP24

NP24

7

NP24

HOLOTYPE

S. bulbulus

NP23

NP23

28

628A-25-1,80-81

S. akropodus (<8)

NP24

30

S. akropodus (<8)

GoM

112

Bergen et al.

Plate 11
NP21

2!m

1

2

NP21

900A-51-6,47-48

S. akropodus

NP21

8.20!m3

900A-51-6,47-48

4900A-51-6,47-48

NP22

S. akropodus

S. peartiae

628A-25-1,80-81

12

GoM

S. peartiae (>7)

NP24

13

14

S. tribulosus

NP24

S. peartiae (>7)

JS20

23

GUYANA

900A-50-5,16-17

15

16

S. tribulosus

S. predistentus

GoM

NP23

900A-50-4,87-88

NP23

8

GoM

18

S. celsus

NP24

900A-49-3,113-114

S. predistentus

10

NP24

Egypt, Nile Delta

NP23

19

20

S. predistentus

NP23

27

628A-26-1,80-81

9S. peartiae

17

NP23

26

NP24

NP24

NP23

25

925A-41-1,16-17

7

S. peartiaeS. predistentus (trans)

NP23

24

NP23

NP23

NP23

NP20

22

6

NP23

NP24

NP20

21

5

S. peartiae

NP23

11

NP23

S. celsus

GoM

NP23

29
NP23

28

NP23

628A-26-1,
80-81

NP23

30